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.     

Striation patterns in serrated blade stabs to cartilage

Stab wounds were made in porcine cartilage with 13 serrated knives, amongst which 4 were drop-point and 9 straight-spine; 9 coarsely serrated, 3 finely serrated and 1 with mixed pattern serrations. The walls of the stab tracks were cast with dental impression material, and the casts photographed together with the knife blades for comparison. All 13 serrated blades produced an "irregularly regular" pattern of striations on cartilage in all stabbings. Unusual and distinctive blade serration patterns produced equally distinctive wound striation patterns. A reference collection of striation patterns and corresponding blades might prove useful for striation pattern analysis. Drop-point blades produced similar striations to straight-spine blades except that the striations were not parallel but rather fan-shaped, converging towards the wound exit. The fan-shaped striation pattern characteristic of drop-point blades is explained by the initial lateral movement of the blade through the cartilage imposed by the presence of the drop point shape. It appears that the greater the overall angle of the drop point, the shorter the blade length over which the drop point occurs, and the closer the first serration is to the knife tip, the more obvious is the fan-shaped pattern. We anticipate that micro-irregularities producing individualising characteristics in non-serrated drop point blades, provided they were located at the tip opposite the drop point, should also show a fan-shaped pattern indicative of a drop point blade. The examination of the walls of stab wounds to cartilage represents an under-utilised source of forensic information to assist in knife identification.     

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.     

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%.     

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.     

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.     

Bullet or bite--a contribution to the morphogenesis of gunshot dermal injury

Histopathologic studies of dermal dog bites revealed changes identical with those observed in distant gunshot skin entrance wounds and in a presternal skin stab wound made by a screwdriver. The similarity of the epithelial and collagen changes produced by these three totally different traumatizing, perforating agencies indicate that it is the bullet's penetrating and crushing power, and not its caloric content, that is responsible for the characteristic dermal collagen changes noted in these common injuries.     

The detection of metallic residues in skin stab wounds by means of SEM-EDS: A pilot study

The morphological analysis of stab wounds may often not be accurate enough to link it with the type of wounding weapon, but a further evaluation may be performed with the search for metallic residues left during the contact between the instrument and the skin. In this study, Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was applied to the study of cadaveric stab wounds performed with kitchen knives composed of iron, chromium and nickel, in order to verify the presence of metallic residues on the wound's edge. Two groups of 10 corpses were selected: group A, including victims of stab wounds and a control group B (died of natural causes). Samplings were performed on the lesions and in intact areas of group A, whereas in group B sampling were performed in non-exposed intact skin. Samples were then analysed with optical microscopy and SEM-EDS. In group A, optical microscopic analysis showed the presence of vital haemorrhagic infiltration, while SEM-EDS showed evidence of microscopic metal traces, isolated or clustered, consisting of iron, chromium and nickel. Moreover, in two cases organic residues of calcium and phosphate were detected, as a probable sign of bone lesion. Control samples (group A in intact areas and group B), were negative for the search of exogenous material to optical microscopy and SEM-EDS. The results show the utility and possible application of the SEM-EDS in theidentification of metallic residues from sharp weapons on the skin.     

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.     

Appearance of injuries caused by machetes and unusually large knives

Machetes (Spanish-American matchets) are sharp, long knives with a broad blade having a slightly curved edge and a thick back. They are used for clearing paths in rough, densely wooded areas. Just like axes and swords they are suitable for causing not only soft tissue wounds, but also deep slashes in the underlying bone. In military conflicts (especially in Central Africa) they are often used as short-range weapons, whereas it is in the nature of things that they are rarely used in Europe. On the basis of 5 cases from the Freiburg material fatal and survived injuries caused by machetes and similarly large knives are discussed. In 2 cases long chop injuries were inflicted on the head causing sharp-edged transections of the bony skullcap; in one case in which the victim survived a broken off part of the blade lodged in the right os parietale. In another 2 cases complete and subtotal decapitation respectively occurred in the victims. As the instrument can be used both for cutting and stabbing there were not only long cutting injuries, but also gaping stab wounds severing the skin over a length of several centimetres; due to the great length of the blade through-and-through wounds were also seen on the trunk. Massive blows with the thick back of the blade caused streak-like bruising.     

Evaluation of atypical stab and incision wounds in a case of combined suicidal injuries

A fatal case of stabbing and cutting is reported which involved a 37-year-old male who suffered from depressive disorder and had already attempted suicide in the past. The postmortem examination revealed 12 lacerations of the scalp, 5 deep incised wounds on the flexor surface of the right forearm, 3 stab wounds of the back of the head, 12 stab wounds of the chest (with cutting of ribs but no injury of heart and lungs), 35 stab wounds of the abdomen and deep incised wounds of both sides of the neck with hesitation marks and incision of the left internal jugular vein. The significance of criteria to properly establish the manner of death like localization, axis and pattern of the wounds, hesitation marks, defense wounds, pulling aside the clothing to expose the target area, sustained capacity of physical activity and potential lethal effects of the single injuries as well as conclusions from the scene of death are discussed.     

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).     

Roentgen imaging of stab wounds in parenchymatous organs

Stab wounds were made in parenchymatous organs (e.g. liver, spleen, kidneys, lungs) using a variety of instruments. The shape of the resulting canal was investigated by X-ray analysis after introduction of an X-ray contrast medium. The best contrast was obtained using a contrast medium containing barium. The shape of the canal gave a direct representation of the outline of the instrument used. The width of the canal was however, always several millimeters smaller than the corresponding blade of the instrument. The position of the blade back in single-edged blades could be demonstrated with stronger contrast.     

An unusual case of suicide by stabbing with a falling weighted dagger.

An unusual suicide by self-stabbing is presented. A 42-year-old man committed suicide with a dagger weighted with 2.72 kg in total and allowed to fall freely. The blade of the dagger fell from a height of 10 cm above the chest, penetrated the second left intercostal skin and pierced the upper lobe of the left lung. However, the weapon did not penetrate the chest skin from a stationary position in our trial at the autopsy. This finding confirms the results of experiments with stab wound dynamics which demonstrated that the impact velocity of the weapon as well as the sharpness of the tip is important for skin penetration.     

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.     

Quantitative analysis of proinflammatory cytokines (IL-1beta, IL-6, TNF-alpha) in human skin wounds

Proinflammatory cytokines play an important role in the mediation of inflammation and trauma. They could be useful for the determination of vitality and wound age. In the present study, 144 human skin wounds due to sharp force were investigated. The material was collected during operations (N=96) and postmortem examinations (N=48). The wound age varied from several seconds or minutes to 9 days. Control skin was available in each individual. The tissue specimens were homogenized and extracted in a solution of PBS and protease inhibitors. Interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) were measured by quantitative ELISA analysis. Statistical evaluation was performed by the t-test using the quotients of levels (wound sample/control skin). In surgical specimens the cytokine levels revealed a clear tendency to increase with wound age. IL-1beta in early skin wounds (24 h, P<0.05). The quantitative analysis of proinflammatory cytokines in wound extracts can contribute to the determination of vitality and wound age, in particular in the very early post-traumatic interval (classic stab wounds).     

The macro- and micromorphological signs of the edge of stabbing-cutting weapons in skin wounds

110 stab-cut skin wounds in 34 dead bodies as well as 38 stab-cut instruments were studied. Three morphologic types of traces left by blade edges of stab-cut instruments, i.e. puncture, microrupture and microcut, were established. Gross and micromorphology of each of these traces depends on the properties of blade edges of stab-cut instruments.     

Fatal and Nonfatal Rip Saw Injuries

This paper deals with a fatal stab wound suffered by a 29-year-old man and nonfatal injuries of 35-year-old and 67-year-old saw operators. Rip saw is a machine that is specially designed for making a rip cut, a cut made parallel to the direction of the wood grain. Rip-saw-related injuries mostly occur when a person is struck by the cutting material, which usually involves splinters of irregular shape and diameter. When the splinter strikes the body diagonally, the injuries may include abrasions, lacerations, and cut wounds; in situations where the victim is struck directly, the most common injuries are oval- or star-shaped stab wounds with a varying width of abrasions around the wounds. Therefore, such injuries may come across as injuries produced by a knife-like instrument, which is an added difficulty in the interpretation of such injuries.     

根据双刃刺器刺创口推断刺器宽度

解决根据皮肤创口推断刺器宽度的问题。实验在自愿捐献的12具男性尸体的胸部,用不同宽度和厚度的双刃匕首致创221个。应用法医学、解剖学及数理统计的理论和技术对创口形成机理、影响因素及其与刺器宽度的相关关系进行分析,得出了以下结论：刺器厚度与创口长度无明显相关,刺器宽度与创口长相关,创口回缩程度与创口方向及刺器宽度相关。并建立了两个最优回归方程,提出了一个根据皮肤双刃利器创口推断刺器宽度的方法。