Forensic Science International 234 (2014) 45–49
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Forensic Science International journal homepage: www.elsevier.com/locate/forsciint
Comparison of stab wound probing versus radiological stab wound channel depiction with contrast medium Stephan A. Bolliger a,b,c,*, Thomas D. Ruder b,c,d, Thomas Ketterer a,b, Nadine Gla¨ser b, Michael J. Thali b,c, Garyfalia Ampanozi b,c a
Institute of Forensic Medicine, Department of Forensic Medicine, Cantonal Hospital, Aarau, Switzerland Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Bern, Switzerland Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Zurich, Switzerland d Institute of Diagnostic, Interventional, and Paediatric Radiology, University Hospital Bern, Switzerland b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 5 November 2012 Received in revised form 3 September 2013 Accepted 17 October 2013 Available online 31 October 2013
Background: Instillation of contrast medium into stab wounds has shown promising results regarding visibility and assessment of general stab direction with computed tomography. However, the accuracy of this method – and, incidentally also probing of stab wounds – has to our knowledge not previously been examined. Also the effect of bluntness of different stabbing objects on the examination of stab wounds was not considered before this study. Methods: Using a pocket-knife, a steak-knife, and a Phillips screwdriver, nine stab wounds each were inflicted to three pork haunches. The depths of the stab wounds were determined by probing and multislice computed tomography (MSCT) after instillation of a contrast medium (CM) and then compared to those observed by dissection, our internal ‘‘gold standard’’. Results: In stab wounds inflicted by knives, MSCT-CM and probing provided results which differed by roughly 10–11% from the dissection results. In screwdriver stabs MSCT-CM showed a deviation of almost 30%, probing over 33%. Discussion: MSCT-CM is a possible alternative to layer-by-layer dissection in autopsy cases of knife stab wounds. Probing, although obsolete in post-mortem examinations, is sufficiently accurate in determining the length of a stab wound of a living person. In cases of stab wounds with blunt objects such as screwdrivers, neither MSCT-CM nor probing proved to be sufficiently accurate. Conclusion: MSCT-CM is a possible alternative to layer-by-layer dissection in autopsy cases of knife stab wounds. Probing, although obsolete in post-mortem examinations, is sufficiently accurate in determining the length of a stab wound of a living person. In cases of stab wounds with blunt objects such as screwdrivers, neither MSCT-CM nor probing proved to be sufficiently accurate. ß 2013 Elsevier Ireland Ltd. All rights reserved.
Keywords: Forensic imaging MSCT Contrast medium Stab channels Virtopsy
1. Introduction At autopsy of deceased stab victims, stab wounds are usually examined by a pain-staking layer-by-layer dissection. This timeconsuming procedure is superior to the now generally obsolete post-mortem probing of injuries, in which previously intact structures may be harmed. In clinical examinations, the stab channel course and depth of supposed ‘‘flesh wounds’’ are still often explored by probing. Radiological imaging is routinely employed in the clinical examination of injuries to the trunk and
* Corresponding author at: Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Zurich, Winterthurerstrasse 190/ 52, CH-8057 Zurich, Switzerland. Tel.: +41 44 6356039. E-mail address: [email protected] (S.A. Bolliger). 0379-0738/$ – see front matter ß 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.forsciint.2013.10.031
head. However, the radiological depiction of a stab channel in softtissue lesions is difficult on post-mortem non-contrast CT [1–5]. As described previously, instillation of contrast medium (CM) into experimentally inflicted stab wounds prior to multislice CT (MSCT) provided very clear images regarding stab direction [6]. As the radiological images were not compared to the actual stab depth, it remained unclear whether this examination technique – in which theoretically bubbles etc. may prevent the contrast medium from seeping into the entire wound – is adequate enough for the determination of stab depths. Equally, it remained unclear if the visibility of a clean, sharp stab channel inflicted by a pocketknife may differ on MSCT-CM from e.g. an injury inflicted by a steak knife or even a rather blunt object such as a screwdriver. We therefore decided to compare the MSCT-CM examination of experimental stab injuries by different stabbing instruments with the current ‘‘gold standard’’, namely dissection.
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S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
As we have had reason to doubt the accuracy of stab wound measurement by probing in the past, we also examined the accuracy of probing compared to dissection. 2. Methods and materials One pork haunch was stabbed nine times with a Swiss Army pocket knife (blade length 6.3 cm, blade width 1.3–1.4 cm, blade thickness 0.05–0.27 cm) (Victorinox A 3610, Victorinox AG, IbachSchwyz, Switzerland), another haunch nine times with a steak
knife (blade length 12 cm, blade width 0.3–1.6 cm) (Slitbar Kitchen Knife, INGKA Holding B.V., Leiden, the Netherlands) and a third haunch again nine times with a Phillips screwdriver (length 10 cm, tip width 0.6 cm) (Swiss Grip PB 8190, PB Swiss Tools GmbH, Wasen im Emmental, Switzerland). Contrast medium (Optiray1 300, Guerbet AG, Zurich, Switzerland) was mixed with the same amount of 0.9% sodium chloride solution. In order to facilitate later photographic documentation of the dissected wound channels, a few millilitres of toluidine blue were added to the contrast medium solution. This
Fig. 1. (a) 3D CT-reconstruction of a pocket-knife stab after instillation of contrast medium. (b) Dissected pocket-knife stab wound. Toluidin blue added to the contrast medium solution made the stab wound more clearly visible.
Fig. 2. (a) 3D CT-reconstruction of a steak-knife stab after instillation of contrast medium. (b) Dissected steak-knife stab wound with Toluidin blue and contrast medium. The shape of the dissected wound resembles more or less the shape of the blade, whereas the CT-reconstruction shows filling defects. This may be due to a lesser volume of contrast medium in these regions, which led to a lesser radioopacity. Regions with less radioopacity were rendered out in the CT-reconstruction, in order to create an image of the stab channel without disturbing surrounding soft-tissue artefacts.
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
47
Fig. 3. (a) 3D CT-reconstruction of a screwdriver stab after instillation of contrast medium. (b) Dissected screwdriver stab wound with Toluidin blue and contrast medium. The dissected stab wound displays a rather straight channel corresponding to the screwdriver, whereas the CT-reconstruction presents a bulge near the entrance. This bulge may be due to contrast-medium seeping into the soft tissue, which is seen in the 3D CT image, but not in the dissected channel, where the bulge may be in a region not seen on the cut surface.
mixture was carefully instilled into each artificial stab wound until the contrast medium (CM) filled the wound completely. Great care was taken not to inject the liquid forcefully. MSCT scanning (Somatom Emotion 6, Siemens AG Medical Solutions, Erlangen, Germany) was performed within minutes after CM instillation on all three haunches with 4 mm 1.25 mm collimation. The reconstruction interval was 0.7 mm. Using a dedicated workstation (Leonardo, Siemens AG Medical Solutions, Erlangen, Germany), a forensic radiologist measured the wound channel depths. After multislice computed tomography with contrast medium (MSCT-CM) was completed, all wounds were manually probed using a knitting needle (0.2 cm diameter) with a blunt tip. Great care was taken not to force the needle into the wound. Dissection of the pork haunches was executed by a boardcertified forensic pathologist by cutting along the long axis of the wound. The results obtained by measuring the depth of the dissected stab channels were regarded as being our internal ‘‘gold standard’’
3. Results 3.1. Pocket knife With the exception of a 2 cm and a 1.5 cm difference, MSCT-CM (Fig. 4 and Table 1) differed 0.5 cm or less compared to the dissection results (mean: 7.16 cm, mean deviation 0.72 cm, SD
Pocket knife
2.5 difference to dissection [cm]
and compared to those obtained by MSCT-CM (Figs. 1–3) and by probing. All deviations from the dissection results were given in positive numbers. Furthermore, the relation of the deviations of MSCT-CM and probing results to the dissection results was calculated. The data were analysed using the Statistical Package for Social Sciences (SPSS PASW 18, SPSS Inc., Chicago, USA). We performed a Shapiro–Wilk test in order to examine the normality of the distribution. The significance of the measurements was tested by performing paired comparisons. p values less than 0.05 indicated statistically significant differences.
2
1.5 1
0.5
MSCT-CM Probe
0
-0.5
1
2
3
4
5
6
7
8
9
-1 -1.5 -2 stab number
Fig. 4. The pocket knife stab depths as measured by the different techniques are shown (results in centimetres).
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
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Steak knife
difference to dissection [cm]
3.5 3 2.5 2 1.5
MSCT-CM probe
1 0.5 0 -0.5
1
2
3
4
5
6
7
8
9
-1 stab number
Fig. 5. The steak knife stab depths as measured by the different techniques are shown (results in centimetres).
0.98 cm, p = 0.870). Probing differed on average 0.83 cm to dissection, with a maximum deviation of 2 cm (mean: 6.38 cm, p = 0.63). 5 of 9 of the probing measurements were greater than dissection and of these, 3 differed by 2 cm. 3 probing results did not differ at all from the dissection results and two measurements were within 0.5 cm of the dissection results. The mean deviation of MSCT-CM amounted to 10.37% of the mean dissection stab length; the probing resulted in 11.14% deviation from dissection. 3.2. Steak knife The mean deviation between MSCT-CM and those of dissection was 0.66 cm (mean: 6.77 cm, SD 0.75 cm, p = 0.219). Probing
Table 1 Pocket-knife stab wounds: Difference between the different examination techniques regarding stab depth measurements and the ‘‘gold standard’’, the dissection. All results are given as positive numbers in centimetres, i.e. a measurement of 2 cm in CT-CM instead of 4 cm as determined by dissection results in ‘‘2 cm’’, not ‘‘–2 cm’’. The symbol ‘‘D’’ refers to the difference of the examination technique to dissection, the symbols ‘‘%D’’ refer to the percentage the difference of the examination technique makes to the total dissection result, regarded as being 100%. Stab. no.
Dissection
DCT-CM
%D CT-CM
DProbe
%D Probe
1 2 3 4 5 6 7 8 9
7.5 6 7.5 7.5 8 6.5 7 8.5 5.5
2 1.5 0.5 0.5 0.5 0.5 0 0.5 0.5
26.6 25 6.6 6.6 6.2 7.6 0 5.8 9
0.5 0 2 2 0.5 0 2 0.5 0
6.6 0 26.6 26.6 6.2 0 28.5 5.8 0
Mean
7.11
0.72
10.37
0.83
11.14
Table 2 Steak knife stab wounds: Difference between the different examination techniques regarding stab depth measurements and the dissection in analogy to Table 1. Stab. no.
Dissection
DCT-CM
1 2 3 4 5 6 7 8 9
8 5.5 7 8 7.5 5.5 7.5 6 9
1 0.5 1 0.5 1.5 0.5 0.5 0.5 0
Mean
7.11
0.666
%D CT-CM 12.5 9 14.2 6.2 20 9 6.6 8.3 0 9.53
DProbe
%D Probe
3 0.5 1 0.5 0.5 0.5 0.5 0.5 0.5
37.5 9 14.2 6.2 6.6 9 6.6 8.3 5.5
0.833
11.43
displayed a mean deviation (Fig. 5 and Table 2) of 0.83 cm (mean: 6.72 cm, SD 1.14 cm, p = 0.336). 5 of 9 MSCT-CM measurements were greater than dissection, and of these, 3 surpassed dissection by 1 cm, with one measurement even surpassing dissection by 2 cm. Probing, on the other hand, showed 6 of 9 measurements within a 0.5 cm range from dissection, one measurement 1 cm greater than dissection and one measurement deviating by 2 cm from the dissection result. When compared to the total depth as measured by dissection, MSCT-CM resulted in a mean deviation of 9.53% and probing of 11.43%. 3.3. Screwdriver MSCT-CM (Fig. 6 and Table 3) achieved a 1.22 cm mean deviation (mean: 5.27 cm, SD 1.15 cm, p = 1.00). The probing method showed a mean deviation of 1.88 cm (mean: 4.05 cm, SD 1.73 cm, p = 0.078). 5 of 9 MSCT-CM measurements were greater than 1 cm or more to the dissection results, and one measurement was 2 and one by 3.5 cm less than dissection. Probing delivered 6 of 9 measurements differing 1 cm or less from dissection. The remaining three probing measurements were more than 3 cm less than dissection. Mean MSCT-CM deviations amounted to 29.52% of the total dissection stab depth, probing, on the other hand, presented a 33.65% mean deviation. 4. Discussion Several limitations of this study deserve comment. First, although our results may be applicable to stab wounds to compact soft tissues (e.g. the extremities or the brain), stab wounds to the chest and abdomen may behave in a different way because the formation of pneumothorax and pneumoperitoneum may distort a
Table 3 Screwdriver stab wounds: Difference between the different examination techniques regarding stab depth measurements and the ‘‘gold standard’’, the dissection, in analogy to Table 1. Stab. no.
Dissection
DCT-CM
%D CT-CM
DProbe
%D Probe
1 2 3 4 5 6 7 8 9
8.5 9 3 1.5 8 3.5 6 7 5
3.5 0 1.5 1.5 2 0.5 0.5 0.5 1
41.1 0 50 100 25 14.2 8.3 7.1 20
5 0.5 1 1 4.5 0 3.5 1 0.5
58.8 5.5 33.3 66.6 56.2 0 58.3 14.2 10
Mean
5.72
1.22
1.88
33.65
29.52
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
Screwdriver
2
difference to dissection [cm]
49
1 0
-1
1
2
3
4
5
6
7
8
9 MSCT-CM
-2
probe
-3 -4 -5 -6 stab number
Fig. 6. The screwdriver stab depths as measured by the different techniques are shown (results in centimetres). Difference between examination technique and dissection results of the pocket-knife stab wounds.
wound channel [7]. Second, it may be criticised that the depth of a stab wound may not reflect the length of a blade. The authors acknowledge that this may be true due to the dynamics of stabbing. However, it was the goal of this study to determine whether MSCT-CM or probing were more accurate to assess the wound depth, not if there was a correlation between wound depth and blade length. The probing of a stab wound – although a rather primitive approach – was surprisingly accurate in stabs with a sharp pocketknife blade and delivered comparable results to the MSCT-CM measurements. Indeed, in these injuries, MSCT-CM displayed mean deviations lying at around 10% and probing roughly 11% of the actual depth, as measured after dissection. MSCT-CM provided similarly accurate results when measuring the stab depth of the serrated steak knife and the pocket-knife wounds, namely 9.53% and 10.37%, respectively. The measurements of the steak-knife stabs by probing did not show statistically relevant differences to those of the pocket-knife (11.14% for the pocket-knife and 11.43% for the steak-knife). If one takes into account the various factors influencing the stab depth in a dynamic setting, we believe that a mean deviation of 10– 11% is nevertheless small enough to permit the drawing of certain reconstructive conclusions. However, this does not apply to the measurements made on stab wounds inflicted by a Phillips screwdriver. The comparatively blunt tip required considerably more force to stab into the haunch and led to a crushing of the tissue, thus giving rise to an irregular, torn and crushed stab channel. The reason for the large deviation (MSCT-CM almost 30%, probing over 33%) in screwdriver stabs is not quite clear; however, most measurements were less than dissection. This may indicate that, in the case of MSCT-CM, some form of wound-obstruction, such as bubbles or torn flesh, could have prevented the contrast medium from completely filling the wound channel, and therefore led to the poor results. Crushed, torn flesh, could also have led to a resistance towards the knitting needle when probing, thus giving rise to the wrong assumption that the end of the stab channel had been reached and therefore a falsely short stab depth concluded. Although deviations of measurements of up to around 11% can, according to our opinion, still be tolerated as being accurate enough, we do not believe that deviations of 30-plus percent are precise enough to draw conclusions on. Summarising the above, measurement accuracy of probing and MSCT-CM are comparable in knife stabs. Probing is cheap and
performed rapidly; however, it bears the risk of dislodging superficially located traces of material into the depth of the wound, which may distort case reconstruction. It also risks damaging previously intact structures. MSCT-CM does not bear these risks; moreover, the data can be reviewed by a different expert group at a later time, should the need arise. This secondlook option is obviously not possible with probing if the body has already been autopsied, cremated or has decomposed. Therefore, we conclude that MSCT-CM is to be preferred to probing, even though both methods deliver comparable results. 5. Conclusion To our opinion, MSCT-CM and probing are adequately accurate when measuring stab wounds inflicted by knives, but not so when stab injuries by blunter objects, such as screwdrivers, are to be examined. Due to the possibility of a later reviewing of the MSCTCM data and the risk of trace displacement and additional injuries in probing, we believe that MSCT-CM is superior to probing. Acknowledgements The authors would like to thank Sandra Mathier, radiology technician, for MSCT scanning. References [1] J. Schnider, M.J.M.J. Thali, S. Ross, L. Oesterhelweg, D. Spendlove, S.A. Bolliger, Injuries due to sharp trauma detected by post-mortem multislice computed tomography (MSCT): a feasibility study, Leg. Med. (Tokyo) 11 (2009) 4–9. [2] S. Bolliger, M.J. Thali, Sharp trauma, in: M.J. Thali, R. Dirnhofer, P.P. Vock (Eds.), The Virtopsy Approach- 3D Optical and Radiological Scanning and Reconstruction in Forensic Medicine, CRC Press, Boca Raton, 2009, pp. 304–317. [3] C.S. De Vries, M. Africa, F.A. Gebremariam, J.J. van Rensburg, S.F. Otto, H.F.H.F. Potgieter, The imaging of stab injuries, Acta Radiol. 51 (2010) 92–106. [4] C. Winskog, Precise wound track measurement requires CAT scan with object in situ: how accurate is post-mortem dissection and evaluation, Forensic Sci. Med. Pathol. 1 (2012) 76–77. [5] M.A. Verhoff, L. Fischer, G. Alzen, F. Ramsthaler, Reconstruction of stab wounds from preoperative CT data – diagnostic report of a clinical forensic examination, Arch. Kriminol. 224 (2009) 73–81. [6] S.A. Bolliger, U. Preiss, N. Glaeser, M.J. Thali, S. Ross, Radiological stab wound channel depiction with instillation of contrast medium, Leg. Med. (Tokyo) 12 (2010) 39–41. [7] T.D. Ruder, T. Ketterer, U. Preiss, M. Bolliger, S. Ross, W.F. Gotsmy, G. Ampanozi, T. Germerott, M.J. Thali, G.M. Hatch, Suicidal knife wound to the heart: challenges in reconstructing wound channels with post mortem CT and CT-angiography, Leg. Med. (Tokyo) 132 (2011) 91–94.
Contents lists available at ScienceDirect
Forensic Science International journal homepage: www.elsevier.com/locate/forsciint
Comparison of stab wound probing versus radiological stab wound channel depiction with contrast medium Stephan A. Bolliger a,b,c,*, Thomas D. Ruder b,c,d, Thomas Ketterer a,b, Nadine Gla¨ser b, Michael J. Thali b,c, Garyfalia Ampanozi b,c a
Institute of Forensic Medicine, Department of Forensic Medicine, Cantonal Hospital, Aarau, Switzerland Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Bern, Switzerland Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Zurich, Switzerland d Institute of Diagnostic, Interventional, and Paediatric Radiology, University Hospital Bern, Switzerland b c
A R T I C L E I N F O
A B S T R A C T
Article history: Received 5 November 2012 Received in revised form 3 September 2013 Accepted 17 October 2013 Available online 31 October 2013
Background: Instillation of contrast medium into stab wounds has shown promising results regarding visibility and assessment of general stab direction with computed tomography. However, the accuracy of this method – and, incidentally also probing of stab wounds – has to our knowledge not previously been examined. Also the effect of bluntness of different stabbing objects on the examination of stab wounds was not considered before this study. Methods: Using a pocket-knife, a steak-knife, and a Phillips screwdriver, nine stab wounds each were inflicted to three pork haunches. The depths of the stab wounds were determined by probing and multislice computed tomography (MSCT) after instillation of a contrast medium (CM) and then compared to those observed by dissection, our internal ‘‘gold standard’’. Results: In stab wounds inflicted by knives, MSCT-CM and probing provided results which differed by roughly 10–11% from the dissection results. In screwdriver stabs MSCT-CM showed a deviation of almost 30%, probing over 33%. Discussion: MSCT-CM is a possible alternative to layer-by-layer dissection in autopsy cases of knife stab wounds. Probing, although obsolete in post-mortem examinations, is sufficiently accurate in determining the length of a stab wound of a living person. In cases of stab wounds with blunt objects such as screwdrivers, neither MSCT-CM nor probing proved to be sufficiently accurate. Conclusion: MSCT-CM is a possible alternative to layer-by-layer dissection in autopsy cases of knife stab wounds. Probing, although obsolete in post-mortem examinations, is sufficiently accurate in determining the length of a stab wound of a living person. In cases of stab wounds with blunt objects such as screwdrivers, neither MSCT-CM nor probing proved to be sufficiently accurate. ß 2013 Elsevier Ireland Ltd. All rights reserved.
Keywords: Forensic imaging MSCT Contrast medium Stab channels Virtopsy
1. Introduction At autopsy of deceased stab victims, stab wounds are usually examined by a pain-staking layer-by-layer dissection. This timeconsuming procedure is superior to the now generally obsolete post-mortem probing of injuries, in which previously intact structures may be harmed. In clinical examinations, the stab channel course and depth of supposed ‘‘flesh wounds’’ are still often explored by probing. Radiological imaging is routinely employed in the clinical examination of injuries to the trunk and
* Corresponding author at: Institute of Forensic Medicine, Department of Forensic Medicine and Imaging, University of Zurich, Winterthurerstrasse 190/ 52, CH-8057 Zurich, Switzerland. Tel.: +41 44 6356039. E-mail address: [email protected] (S.A. Bolliger). 0379-0738/$ – see front matter ß 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.forsciint.2013.10.031
head. However, the radiological depiction of a stab channel in softtissue lesions is difficult on post-mortem non-contrast CT [1–5]. As described previously, instillation of contrast medium (CM) into experimentally inflicted stab wounds prior to multislice CT (MSCT) provided very clear images regarding stab direction [6]. As the radiological images were not compared to the actual stab depth, it remained unclear whether this examination technique – in which theoretically bubbles etc. may prevent the contrast medium from seeping into the entire wound – is adequate enough for the determination of stab depths. Equally, it remained unclear if the visibility of a clean, sharp stab channel inflicted by a pocketknife may differ on MSCT-CM from e.g. an injury inflicted by a steak knife or even a rather blunt object such as a screwdriver. We therefore decided to compare the MSCT-CM examination of experimental stab injuries by different stabbing instruments with the current ‘‘gold standard’’, namely dissection.
46
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
As we have had reason to doubt the accuracy of stab wound measurement by probing in the past, we also examined the accuracy of probing compared to dissection. 2. Methods and materials One pork haunch was stabbed nine times with a Swiss Army pocket knife (blade length 6.3 cm, blade width 1.3–1.4 cm, blade thickness 0.05–0.27 cm) (Victorinox A 3610, Victorinox AG, IbachSchwyz, Switzerland), another haunch nine times with a steak
knife (blade length 12 cm, blade width 0.3–1.6 cm) (Slitbar Kitchen Knife, INGKA Holding B.V., Leiden, the Netherlands) and a third haunch again nine times with a Phillips screwdriver (length 10 cm, tip width 0.6 cm) (Swiss Grip PB 8190, PB Swiss Tools GmbH, Wasen im Emmental, Switzerland). Contrast medium (Optiray1 300, Guerbet AG, Zurich, Switzerland) was mixed with the same amount of 0.9% sodium chloride solution. In order to facilitate later photographic documentation of the dissected wound channels, a few millilitres of toluidine blue were added to the contrast medium solution. This
Fig. 1. (a) 3D CT-reconstruction of a pocket-knife stab after instillation of contrast medium. (b) Dissected pocket-knife stab wound. Toluidin blue added to the contrast medium solution made the stab wound more clearly visible.
Fig. 2. (a) 3D CT-reconstruction of a steak-knife stab after instillation of contrast medium. (b) Dissected steak-knife stab wound with Toluidin blue and contrast medium. The shape of the dissected wound resembles more or less the shape of the blade, whereas the CT-reconstruction shows filling defects. This may be due to a lesser volume of contrast medium in these regions, which led to a lesser radioopacity. Regions with less radioopacity were rendered out in the CT-reconstruction, in order to create an image of the stab channel without disturbing surrounding soft-tissue artefacts.
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
47
Fig. 3. (a) 3D CT-reconstruction of a screwdriver stab after instillation of contrast medium. (b) Dissected screwdriver stab wound with Toluidin blue and contrast medium. The dissected stab wound displays a rather straight channel corresponding to the screwdriver, whereas the CT-reconstruction presents a bulge near the entrance. This bulge may be due to contrast-medium seeping into the soft tissue, which is seen in the 3D CT image, but not in the dissected channel, where the bulge may be in a region not seen on the cut surface.
mixture was carefully instilled into each artificial stab wound until the contrast medium (CM) filled the wound completely. Great care was taken not to inject the liquid forcefully. MSCT scanning (Somatom Emotion 6, Siemens AG Medical Solutions, Erlangen, Germany) was performed within minutes after CM instillation on all three haunches with 4 mm 1.25 mm collimation. The reconstruction interval was 0.7 mm. Using a dedicated workstation (Leonardo, Siemens AG Medical Solutions, Erlangen, Germany), a forensic radiologist measured the wound channel depths. After multislice computed tomography with contrast medium (MSCT-CM) was completed, all wounds were manually probed using a knitting needle (0.2 cm diameter) with a blunt tip. Great care was taken not to force the needle into the wound. Dissection of the pork haunches was executed by a boardcertified forensic pathologist by cutting along the long axis of the wound. The results obtained by measuring the depth of the dissected stab channels were regarded as being our internal ‘‘gold standard’’
3. Results 3.1. Pocket knife With the exception of a 2 cm and a 1.5 cm difference, MSCT-CM (Fig. 4 and Table 1) differed 0.5 cm or less compared to the dissection results (mean: 7.16 cm, mean deviation 0.72 cm, SD
Pocket knife
2.5 difference to dissection [cm]
and compared to those obtained by MSCT-CM (Figs. 1–3) and by probing. All deviations from the dissection results were given in positive numbers. Furthermore, the relation of the deviations of MSCT-CM and probing results to the dissection results was calculated. The data were analysed using the Statistical Package for Social Sciences (SPSS PASW 18, SPSS Inc., Chicago, USA). We performed a Shapiro–Wilk test in order to examine the normality of the distribution. The significance of the measurements was tested by performing paired comparisons. p values less than 0.05 indicated statistically significant differences.
2
1.5 1
0.5
MSCT-CM Probe
0
-0.5
1
2
3
4
5
6
7
8
9
-1 -1.5 -2 stab number
Fig. 4. The pocket knife stab depths as measured by the different techniques are shown (results in centimetres).
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
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Steak knife
difference to dissection [cm]
3.5 3 2.5 2 1.5
MSCT-CM probe
1 0.5 0 -0.5
1
2
3
4
5
6
7
8
9
-1 stab number
Fig. 5. The steak knife stab depths as measured by the different techniques are shown (results in centimetres).
0.98 cm, p = 0.870). Probing differed on average 0.83 cm to dissection, with a maximum deviation of 2 cm (mean: 6.38 cm, p = 0.63). 5 of 9 of the probing measurements were greater than dissection and of these, 3 differed by 2 cm. 3 probing results did not differ at all from the dissection results and two measurements were within 0.5 cm of the dissection results. The mean deviation of MSCT-CM amounted to 10.37% of the mean dissection stab length; the probing resulted in 11.14% deviation from dissection. 3.2. Steak knife The mean deviation between MSCT-CM and those of dissection was 0.66 cm (mean: 6.77 cm, SD 0.75 cm, p = 0.219). Probing
Table 1 Pocket-knife stab wounds: Difference between the different examination techniques regarding stab depth measurements and the ‘‘gold standard’’, the dissection. All results are given as positive numbers in centimetres, i.e. a measurement of 2 cm in CT-CM instead of 4 cm as determined by dissection results in ‘‘2 cm’’, not ‘‘–2 cm’’. The symbol ‘‘D’’ refers to the difference of the examination technique to dissection, the symbols ‘‘%D’’ refer to the percentage the difference of the examination technique makes to the total dissection result, regarded as being 100%. Stab. no.
Dissection
DCT-CM
%D CT-CM
DProbe
%D Probe
1 2 3 4 5 6 7 8 9
7.5 6 7.5 7.5 8 6.5 7 8.5 5.5
2 1.5 0.5 0.5 0.5 0.5 0 0.5 0.5
26.6 25 6.6 6.6 6.2 7.6 0 5.8 9
0.5 0 2 2 0.5 0 2 0.5 0
6.6 0 26.6 26.6 6.2 0 28.5 5.8 0
Mean
7.11
0.72
10.37
0.83
11.14
Table 2 Steak knife stab wounds: Difference between the different examination techniques regarding stab depth measurements and the dissection in analogy to Table 1. Stab. no.
Dissection
DCT-CM
1 2 3 4 5 6 7 8 9
8 5.5 7 8 7.5 5.5 7.5 6 9
1 0.5 1 0.5 1.5 0.5 0.5 0.5 0
Mean
7.11
0.666
%D CT-CM 12.5 9 14.2 6.2 20 9 6.6 8.3 0 9.53
DProbe
%D Probe
3 0.5 1 0.5 0.5 0.5 0.5 0.5 0.5
37.5 9 14.2 6.2 6.6 9 6.6 8.3 5.5
0.833
11.43
displayed a mean deviation (Fig. 5 and Table 2) of 0.83 cm (mean: 6.72 cm, SD 1.14 cm, p = 0.336). 5 of 9 MSCT-CM measurements were greater than dissection, and of these, 3 surpassed dissection by 1 cm, with one measurement even surpassing dissection by 2 cm. Probing, on the other hand, showed 6 of 9 measurements within a 0.5 cm range from dissection, one measurement 1 cm greater than dissection and one measurement deviating by 2 cm from the dissection result. When compared to the total depth as measured by dissection, MSCT-CM resulted in a mean deviation of 9.53% and probing of 11.43%. 3.3. Screwdriver MSCT-CM (Fig. 6 and Table 3) achieved a 1.22 cm mean deviation (mean: 5.27 cm, SD 1.15 cm, p = 1.00). The probing method showed a mean deviation of 1.88 cm (mean: 4.05 cm, SD 1.73 cm, p = 0.078). 5 of 9 MSCT-CM measurements were greater than 1 cm or more to the dissection results, and one measurement was 2 and one by 3.5 cm less than dissection. Probing delivered 6 of 9 measurements differing 1 cm or less from dissection. The remaining three probing measurements were more than 3 cm less than dissection. Mean MSCT-CM deviations amounted to 29.52% of the total dissection stab depth, probing, on the other hand, presented a 33.65% mean deviation. 4. Discussion Several limitations of this study deserve comment. First, although our results may be applicable to stab wounds to compact soft tissues (e.g. the extremities or the brain), stab wounds to the chest and abdomen may behave in a different way because the formation of pneumothorax and pneumoperitoneum may distort a
Table 3 Screwdriver stab wounds: Difference between the different examination techniques regarding stab depth measurements and the ‘‘gold standard’’, the dissection, in analogy to Table 1. Stab. no.
Dissection
DCT-CM
%D CT-CM
DProbe
%D Probe
1 2 3 4 5 6 7 8 9
8.5 9 3 1.5 8 3.5 6 7 5
3.5 0 1.5 1.5 2 0.5 0.5 0.5 1
41.1 0 50 100 25 14.2 8.3 7.1 20
5 0.5 1 1 4.5 0 3.5 1 0.5
58.8 5.5 33.3 66.6 56.2 0 58.3 14.2 10
Mean
5.72
1.22
1.88
33.65
29.52
S.A. Bolliger et al. / Forensic Science International 234 (2014) 45–49
Screwdriver
2
difference to dissection [cm]
49
1 0
-1
1
2
3
4
5
6
7
8
9 MSCT-CM
-2
probe
-3 -4 -5 -6 stab number
Fig. 6. The screwdriver stab depths as measured by the different techniques are shown (results in centimetres). Difference between examination technique and dissection results of the pocket-knife stab wounds.
wound channel [7]. Second, it may be criticised that the depth of a stab wound may not reflect the length of a blade. The authors acknowledge that this may be true due to the dynamics of stabbing. However, it was the goal of this study to determine whether MSCT-CM or probing were more accurate to assess the wound depth, not if there was a correlation between wound depth and blade length. The probing of a stab wound – although a rather primitive approach – was surprisingly accurate in stabs with a sharp pocketknife blade and delivered comparable results to the MSCT-CM measurements. Indeed, in these injuries, MSCT-CM displayed mean deviations lying at around 10% and probing roughly 11% of the actual depth, as measured after dissection. MSCT-CM provided similarly accurate results when measuring the stab depth of the serrated steak knife and the pocket-knife wounds, namely 9.53% and 10.37%, respectively. The measurements of the steak-knife stabs by probing did not show statistically relevant differences to those of the pocket-knife (11.14% for the pocket-knife and 11.43% for the steak-knife). If one takes into account the various factors influencing the stab depth in a dynamic setting, we believe that a mean deviation of 10– 11% is nevertheless small enough to permit the drawing of certain reconstructive conclusions. However, this does not apply to the measurements made on stab wounds inflicted by a Phillips screwdriver. The comparatively blunt tip required considerably more force to stab into the haunch and led to a crushing of the tissue, thus giving rise to an irregular, torn and crushed stab channel. The reason for the large deviation (MSCT-CM almost 30%, probing over 33%) in screwdriver stabs is not quite clear; however, most measurements were less than dissection. This may indicate that, in the case of MSCT-CM, some form of wound-obstruction, such as bubbles or torn flesh, could have prevented the contrast medium from completely filling the wound channel, and therefore led to the poor results. Crushed, torn flesh, could also have led to a resistance towards the knitting needle when probing, thus giving rise to the wrong assumption that the end of the stab channel had been reached and therefore a falsely short stab depth concluded. Although deviations of measurements of up to around 11% can, according to our opinion, still be tolerated as being accurate enough, we do not believe that deviations of 30-plus percent are precise enough to draw conclusions on. Summarising the above, measurement accuracy of probing and MSCT-CM are comparable in knife stabs. Probing is cheap and
performed rapidly; however, it bears the risk of dislodging superficially located traces of material into the depth of the wound, which may distort case reconstruction. It also risks damaging previously intact structures. MSCT-CM does not bear these risks; moreover, the data can be reviewed by a different expert group at a later time, should the need arise. This secondlook option is obviously not possible with probing if the body has already been autopsied, cremated or has decomposed. Therefore, we conclude that MSCT-CM is to be preferred to probing, even though both methods deliver comparable results. 5. Conclusion To our opinion, MSCT-CM and probing are adequately accurate when measuring stab wounds inflicted by knives, but not so when stab injuries by blunter objects, such as screwdrivers, are to be examined. Due to the possibility of a later reviewing of the MSCTCM data and the risk of trace displacement and additional injuries in probing, we believe that MSCT-CM is superior to probing. Acknowledgements The authors would like to thank Sandra Mathier, radiology technician, for MSCT scanning. References [1] J. Schnider, M.J.M.J. Thali, S. Ross, L. Oesterhelweg, D. Spendlove, S.A. Bolliger, Injuries due to sharp trauma detected by post-mortem multislice computed tomography (MSCT): a feasibility study, Leg. Med. (Tokyo) 11 (2009) 4–9. [2] S. Bolliger, M.J. Thali, Sharp trauma, in: M.J. Thali, R. Dirnhofer, P.P. Vock (Eds.), The Virtopsy Approach- 3D Optical and Radiological Scanning and Reconstruction in Forensic Medicine, CRC Press, Boca Raton, 2009, pp. 304–317. [3] C.S. De Vries, M. Africa, F.A. Gebremariam, J.J. van Rensburg, S.F. Otto, H.F.H.F. Potgieter, The imaging of stab injuries, Acta Radiol. 51 (2010) 92–106. [4] C. Winskog, Precise wound track measurement requires CAT scan with object in situ: how accurate is post-mortem dissection and evaluation, Forensic Sci. Med. Pathol. 1 (2012) 76–77. [5] M.A. Verhoff, L. Fischer, G. Alzen, F. Ramsthaler, Reconstruction of stab wounds from preoperative CT data – diagnostic report of a clinical forensic examination, Arch. Kriminol. 224 (2009) 73–81. [6] S.A. Bolliger, U. Preiss, N. Glaeser, M.J. Thali, S. Ross, Radiological stab wound channel depiction with instillation of contrast medium, Leg. Med. (Tokyo) 12 (2010) 39–41. [7] T.D. Ruder, T. Ketterer, U. Preiss, M. Bolliger, S. Ross, W.F. Gotsmy, G. Ampanozi, T. Germerott, M.J. Thali, G.M. Hatch, Suicidal knife wound to the heart: challenges in reconstructing wound channels with post mortem CT and CT-angiography, Leg. Med. (Tokyo) 132 (2011) 91–94.
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