Tool mark striations in pig skin produced by stabs from a serrated blade

Stab wounds produced by serrated blades are generally indistinguishable from stab wounds produced by non-serrated blades, except when visible tool mark striations are left on severed cartilage. Using a pig-skin experimental model, we explored the possibility that similar striations may be left in skin. Stabs into pig skin were made using a straight spine coarsely serrated blade (121), a drop point finely serrated blade (20), a clip point irregular coarsely serrated blade (20), a drop point coarsely serrated blade (15), and as controls 2 non-serrated blades (40). Tool mark striations could be seen on the skin wall of the stab canal in all stabs made using serrated blades but in none with non-serrated blades.The striation pattern, reflecting the class characteristics of the serrated blade, was the same as that described in cartilage but less well defined. Fixation of the specimen with Carnoy's solution best preserved visible striations, and fixation with formaldehyde after staining with 5% Neutral Red was also satisfactory. Casting with vinyl polysiloxane dental impression material greatly facilitated photo-documentation. Applying the technique to homicidal stabbings may help identify stab wounds produced with serrated blades.     

Virtual casting of stab wounds in cartilage using micro-computed tomography

In homicidal stabbings using a serrated knife, stab wounds involving costal cartilage leave striations on the cut surface of the cartilage from the serration points on the blade edge. Class characteristics of the serrated blade can be determined from the striation marks, and individualizing characteristics may be seen also. The traditional method for recording the striation marks involves the pernickety technique of casting with dental impression material. We assessed the potential utility of micro-computed tomography scanning of the stab track as a technique for nondestructive recording of striation patterns and virtual casting of them. Stab tracks in porcine cartilage, produced with a coarsely serrated blade, were scanned with a bench-top micro-computed tomography scanner. The typical irregularly regular striation pattern could be demonstrated, and the images manipulated, using proprietary software to produce a virtual cast. Whether the technology will have sufficient resolution to image not only class characteristic tool marks but also the much finer individualizing tool marks remains to be evaluated, but the technology shows considerable promise.     

An experimental model of tool mark striations in soft tissues produced by serrated blades

Stab wounds produced by serrated blades are generally indistinguishable from stab wounds produced by non-serrated blades, except when visible tool mark striations are left on severed cartilage. We explored the possibility that similar striations may be produced on the soft tissues of internal organs. Loin of beef, bovine kidney, and pig heart, liver, and aorta were each stabbed 20 times with a coarsely serrated blade. The walls of the stab tracks were exposed and documented by photography, cast with dental impression material, and the casts photographed. Striations were identified in all of the tissues in every stabbing, but their consistency and quality varied between tissues. Striations were most easily seen in liver, heart, and aorta. Tool mark striations in soft tissues other than cartilage have not been described in homicidal stabbings, likely because they have not been sought. We suggest that the walls of stab wound tracks should be exposed, and tissue striations should be sought as a means of identifying the weapon as having a serrated blade.     

Microscopic Analysis of Sharp Force Trauma in Bone and Cartilage: A Validation Study,,

Sharp force trauma research lacks agreement on reported error rates for correctly identifying toolmark characteristics on bone and cartilage. This study provides error rates for determining blade class (serrated, partially serrated, nonserrated) and type of edge bevel (left, right, even). Three analysts examined cuts to a wax medium, cartilage, and bone using two types of microscopes. Additionally, the observers examined impressions taken from the wax medium and the cartilage. Overall, a total of 504 observations were performed. Serrated blades were distinguishable from nonserrated blades due to their patterned striations. Some difficulties were encountered in distinguishing serrated and partially serrated blades; however, when these groups were considered together as one classification type (serrated), classification accuracy improved from 79% to 96%. Classification accuracy for edge bevel was 65%. Error rates were similar when comparing direct observation of the cut marks versus indirect observation (impressions). Additionally, the type of microscope used did not affect error rates.     

Validation of tool mark analysis of cut costal cartilage

This study was designed to establish the potential error rate associated with the generally accepted method of tool mark analysis of cut marks in costal cartilage. Three knives with different blade types were used to make experimental cut marks in costal cartilage of pigs. Each cut surface was cast, and each cast was examined by three analysts working independently. The presence of striations, regularity of striations, and presence of a primary and secondary striation pattern were recorded for each cast. The distance between each striation was measured. The results showed that striations were not consistently impressed on the cut surface by the blade's cutting edge. Also, blade type classification by the presence or absence of striations led to a 65% misclassification rate. Use of the classification tree and cross-validation methods and inclusion of the mean interstriation distance decreased the error rate to c. 50%.     

Intracranial stab injuries: case report and case study

Non-missile penetrating brain injuries are rare events in western countries. We report a case with lethal stab injury of the brain and identification of the weapon used in the assault by digital superimposition on CT scans taken at admission of the victim to a hospital. Furthermore, all cases with knife stab wounds of the skull between 1971 and 2000 were analyzed and compared with literature reports. Results of this study show that there is no region preference despite of differences in bone thickness, that stab wounds of the brain are almost invariably associated with multiple stab wounds to the trunk and that the wound tract may correspond to the dimensions of the blade allowing the identification of the weapon by digital image analysis.     

Macroscopic and microscopic analysis of knife stab wounds on fleshed and clothed ribs

Stab wounds upon bone are analyzed to interpret the weapon used and the physical context in which the attack occurred. The literature demonstrates that most research conducted pertaining to wound patterns has been carried out on defleshed and unclothed bone samples, not adequately replicating actual circumstances. For this research, six half pig torsos (Sus scrofa), fleshed (including muscle, fat, epidermis, and dermis layers) and clothed, were stabbed using three knife types, applying both straight and downward thrusts. Analysis conducted macroscopically and through a scanning electron microscope with an environmental secondary electron detector revealed a general lack of consistency in wound pattern and associated secondary effects. Consequently, it was not possible to establish wound pattern per knife type as suggested in previous research or relate it to stab motion. Advantage of microscopic analysis was evident in recognizing wound traits and observation of trace evidence not visible macroscopically.     

On a knife edge: A preliminary investigation of clothing damage using rounded-tip knives

Bladed weapons are frequently encountered in violent crime offences including street based and armed robberies, murder, sexual assaults and terrorism. A study was conducted involving four frequently encountered clothing fabrics: t-shirt (knitted cotton), denim jeans (twill woven cotton), long sleeved top (knitted synthetic blend), and skirt (non-woven faux leather) and five knives to investigate any damage resulting from a downward stabbing motion, with 300 stabs in total. Any resultant penetrating severance damage was then photographed, measured and analysed. Statistical analysis revealed significant differences between the stab hole size and shape, as a consequence of the design of a bladed weapon (in particular, the tip shape) that caused it. There is a notable correlation between the Assure knife (rounded tip) and no resulting severance damage, as the fabric surfaces were not breached with this knife. This suggests a clear alternative to pointed tip knife blades. These findings will be of interest to investigators of knife crime offences, crime-reduction units, knife manufacturers and practitioners, who share the goal of identifying a safer alternative to conventional knife blade design.     

捅创论(附尸检例报告)

无尖无刃的细长钝器,沿其长轴戳入人体形成的创伤应命名为捅创。国内外现有的法医学书籍很少甚至没有描述过此创,个别作者将其归入锐器刺创。本文作者通过案例研究发现:不仅该创的致伤物为无刃无尖的棍棒类钝器(如木棍、木桩、手杖、擀面棍、铁锹把、竹竿、筷子、钢筋)而且成伤机制、形态学变化也与锐器刺创不同,应属于钝器伤。     

Morphologic, experimental-comparative investigation as an identification of the injuring instrument method

Aiming to identify the injuring tool characteristics and the tool itself morphologic, experimental-comparative investigations of the skin wound, rib and cartilage injuries taken during the autopsy are performed. During 1995-2004, 489 investigations were performed for this purpose. In 418 cases, knives were submitted for identification of the specific injuring tool (in total-835 knives). In 205 cases the investigation included not only skin wounds, but also the injured rib cartilages. Identification investigations were performed by investigating both the skin wounds morphologic characteristics and dynamic traces-trails in the rib cartilage tissue left by the micro relief of the knife blade edge. In the case of the investigated and experimental skin wounds characteristics coincidence the experimental and comparative dynamic traces investigation was performed when the traces were suitable for the tool identification purposes. In the case of the investigated and experimental skin wounds, dynamic traces coincidence, the totality of the coincided characteristics was considered individual. In those cases, the conclusion included the fact that the injury had been made by a particular knife. According to our data during 1995-2004 in 23 cases-15.9% (5.5% out of the total investigated cases), the knife identification was based on the skin wound characteristics and dynamic traces in the rib cartilage tissue. In our opinion, the dynamic traces in the rib cartilage tissue investigations supplement the identification field and are valuable in the tool identification. In 11 (2.6% out of the total investigated cases) cases knives were identified only by the skin wounds morphologic characteristics, the ribs being not injured or dynamic traces being not suitable for the tool identification.     

Immunocytochemical examination of biological traces on knife blades

In cases of penetrating stab wounds by different knives it is highly relevant to prove which knife caused which injury, especially if one of the injuries was lethal. This is possible by immunocytochemical examination of cellular material remaining on the injuring blade because some organs have organ-specific antigen determinants such as alpha-l-fetoprotein in the liver cells or cardiac troponin I in the heart muscle cells, to which antibodies can bind. Even when penetrations occur through several layers of clothing, enough cells from the injured organ remain on the blade of a knife to allow immunohistochemical examination. These cells can be collected by means of adhesive film or wiping the blade and can be stained immunocytochemically. The organ specificity of the examined proteins allows proof of their origin. The present study shows that immunocytochemical alpha-l-fetoprotein and cardiac troponin I staining of the cells remaining on a knife blade enables proof of whether the knife blade injured the heart or the liver, or both.     

Chronology of a homicide and an attempted suicide by DNA analysis of selected blood stains on the weapon (knife)]

A five-year-old boy was fatally injured by a stab and a cut to the throat. The suspected offender, an acquaintance of the victim's mother, stated that he had been disturbed by the boy while attempting suicide and had therefore killed the boy. The suspect showed superficial cuts on both wrists and three shallow stabs on the right-hand side of the abdomen. The purpose of the forensic investigations was to answer the question if the suspect's statement could be confirmed or if the attempted suicide took place after killing the boy. The blood-smeared blade of the knife was divided into different sectors with the cutting edge and the tip of the blade being examined separately from the sides. The blood traces from the different blade sectors were then typed in 12 different DNA regions by PCR (polymerase-chain-reaction). It could be demonstrated that the strong blood traces on the sides of the blade originated from the victim alone, whereas in the area of the edge and the tip of the blade the amount of the victim's blood was negligible compared with that of the suspected offender. The explanation for this finding is that in the areas of the edge and the tip of the knife the blood of the victim must have been replaced by the blood of the suspected perpetrator, which means that the suicidal injuries were the last to be caused by the knife.     

A transnasal intracranial stab wound by a plastic-covered umbrella tip

A 48-year-old man died from a transnasal intracranial stab wound caused by an umbrella. The track of the stab passed from the right nostril, through the sphenoid sinus, the left side of the sella turcica and anterior clinoid process, and finally reached the surface of the brain. The stab wound crossed the left internal carotid artery, causing an exsanguination and aspiration of blood into the airway, resulting in death. It is extremely rare that an umbrella tip used during a struggle would stab the nostril of the victim. Transnasal intracranial stab wounds can be overlooked and require sensitive handling.     

Puncture wounds caused by glass mistaken for with stab wounds with a knife

Three cases are presented where fatal puncture wounds caused by broken glass were very similar to stab wounds inflicted by a knife with a single-edged blade. Thus, all three cases caused a murder investigation to be initiated. It could only be determined that these wounds had been caused by glass after a detailed forensic autopsy. In two of the three cases, the only evidence for this was the identification of glass fragments in the wounds. The importance of X-ray examinations is underlined because modern glass in common use is radiopaque. Glass fragments lodged in the wounds can reduce the loss of blood and thus, prolong the capacity to act despite severe injuries.     

Defined contusion marks caused by the knife handle]

If in inflicting a stab wound the knife is vigorously pushed in up to the end of the blade, this does not only cause cutting of the tissue, but also a blunt traumatization. The resulting abrasions can correspond with the respective construction parts (handle, handguard, devices for fixing the open blade) as to position, shape and size, thus allowing conclusions as to the shape of the instrument used. Incomplete, one-sided marks of the handle suggest an oblique-angled stab. The presence of a contusion mark shows that the blade penetrated completely, which makes it easier to draw conclusions as to the length of the blade from the depth of penetration. The reconstruction possibilities are demonstrated on the basis of three autopsies (homicide cases with different types of knives).     

Suicidal incised wound of a fistula for hemodialysis access in an elderly woman: case report

A very rare case of suicide by stab wound of a fistula for hemodialysis access in an elderly woman is reported. The incidence of suicide attempts in people undergoing hemodialysis is well known. Nevertheless, suicide means do not usually include stab wounds of the arteriovenous access. Various pattern differences between homicidal and suicidal stab wounds, characteristics of suicide in the elderly, and approaches to the investigation of such cases are briefly discussed.     

An unusual homicide case with subsequent suicide

In the medicolegal literature reports on homicides followed by suicide, especially in elderly people, are rare. In the present case, the victim, a 79-year-old woman, showed a rather unusual injury pattern: 3 gunshots to the head (with only 2 entrance wounds and 3 intracranial projectiles) and 2 stabs from a knife. The tools used for inflicting the stab wounds (a hunting knife and a double-edged dagger) were left in the victim's body after the offense. The 89-year-old husband hanged himself with an aerial cable after killing his wife. The police investigations and the autopsy findings suggested a combined homicide-suicide. The motive for the offense could be a so-called delusion of poverty associated with symptoms of depression.     

Frequency of bone/cartilage lesions in stab and incised wounds fatalities

A retrospective study was carried out on 58 fatalities due to stab or incised wounds. The frequency of bone or cartilage lesions was analysed according to the number of wounds, the circumstances of death and the anatomical site. Our findings showed that bone/cartilage lesions were present in about 53% of the cases. Cartilage lesions were more frequent than bone lesions. The mean number of wounds in the group with bone/cartilage lesions was statistically higher than the mean number of wounds in the group without lesions (P=0.0068). The main cause of death was thoracic injury in the groups with and without bone/cartilage lesions. In case of skeletal remains, only bone or cartilage lesions allow to diagnose stab or incised wounds. The discovery of these lesions, often of small size, justifies a complete and careful examination of skeletal remains with the help of stereomicroscopy.     

Estimation of bullet striation similarity using neural networks

A new method that searches for similar striation patterns using neural networks is described. Neural networks have been developed based on the human brain, which is good at pattern recognition. Therefore, neural networks would be expected to be effective in identifying striated toolmarks on bullets. The neural networks used in this study deal with binary signals derived from striation images. This signal plays a significant role in identification, because this signal is the key to the individually of the striations. The neural network searches a database for similar striations by means of these binary signals. The neural network used here is a multilayer network consisting of 96 neurons in the input layer, 15 neurons in the middle, and one neuron in the output layer. Two signals are inputted into the network and a score is estimated based on the similarity of these signals. For this purpose, the network is assigned to a previous learning. To initially test the validity of the procedure, the network identifies artificial patterns that are randomly produced on a personal computer. The results were acceptable and showed robustness for the deformation of patterns. Moreover, with ten unidentified bullets and ten database bullets, the network consistently was able to select the correct pair.     

Secondary combined suicide viewed by the wife]

A 47-year-old man was found dead at the bottom of a wall outward the door of the cellar of his house. Preliminary physical examination at the scene of the death revealed a laceration of the scalp, an incised wound in front of the neck and several stab wounds in the left chest penetrating through the clothing. Questioned by the police his wife told that her husband who suffered from severe depression had inflicted the incised and the stab wounds himself, had made an unsuccessful attempt at self-strangulation and had finally jumped down from the wall beside the stairs declining to the cellar of their house. As the circumstances of the scenario were suspicious and as the pattern of injuries arose doubts concerning self-infliction homicide was taken into consideration as well. Autopsy showed additional hesitation marks adjacent to the left end of the incised wound in front of the neck. The stab wounds of the chest were restricted to the region of the heart and displayed only minimal penetration of the chest-wall, findings characteristic of self-infliction. As a consequence the manner of death could be determined as prolonged suicide, and exact reconstruction was possible with the help of the wife's testimony.