A pilot study examining garment severance damage caused by a trained sharp-weapon user

Abstract

The pilot study summarized in this paper aimed to raise awareness of a gap that exists in the forensic textile science literature about damage caused to clothing by trained sharp-weapon users. A male trained in the Filipino martial arts discipline of Eskrima performed attack techniques on a physical model of a male torso covered with a 97% cotton/3% elastane knitted T-shirt, that is, a garment commonly worn by males. Fabric severance appearance created by three different, but commonly available, knives was evaluated. High-speed video was used to capture each attack. After each attack the resulting damage to the garment was assessed. This pilot study highlighted differences in severances associated with weapon selection, that is, not all knives resulted in similar patterns of textile damage. In addition, a mixture of stab and slash severances were observed. The findings demonstrated the possible misinterpretation of textile damage under these circumstances compared to damage patterns reported in the existing forensic textile science literature for more commonly occurring knife attacks (i.e. stabbings).

Keywords

textile damage simulant T-shirt martial arts knife

Knives are the predominant weapon used in homicides in England and Wales.¹ During a domestic or unplanned incident, a weapon of convenience is typically used by a person inexperienced in the use of knives (e.g. a kitchen knife). However, in some cases, and particularly in premeditated attacks, the purchase of a specific knife may occur, and that weapon may be used by someone with a level of professional expertise.^2–4

Diverse groups of people use sharp weapons (i.e. knives, spears, swords) professionally. Examples include military personnel, martial arts practitioners and historical re-enactment groups (for example, The Vikings and The Sealed Knot.^5,6) The training received by these individuals affects how the sharp weapon is used, how long an attack might take and the area of the body targeted.^7–9 The numerous books that describe elements of sharp-weapon usage can be broadly divided into historical discussions, military tactics, indigenous techniques and martial arts.^7–11 Within most reputable martial arts schools sharp-weapon training is generally reserved for people who have reached a certain level of competence (e.g. first-level black belt). This ensures that an individual’s character and temperament can be assessed and unsuitable candidates excluded from training. This is not the case with sharp-weapon training and anatomical targeting information freely available via the internet.

People who are victims in sharp-weapon attacks are usually clothed. Damage occurs to clothing layers typically in the torso region of the body and this is forensically important with respect to weapon identification.^3,12–18 An awareness of fiber composition and fabric and garment structure, and how these variables affect textile damage, have become increasingly important in forensic textile science.^19–21 Injuries sustained during a sharp-weapon attack may be either classified as stab or incised (slash) wounds, and both may occur during a single attack.¹⁶ The forensic textile science literature includes studies evaluating fabric severance created from sharp weapons,^21–25 although no studies appear to exist that examine severances caused by an expert in sharp-weapon use. The majority of previous studies have concentrated on damage inflicted by a single penetrating stab impact, even though homicides usually involve more than one wound.¹⁷ Fewer details with respect to damage caused by slash cuts have been reported. These are usually described as occurring by two different actions: (i) chop and drag and (ii) sweeping slash.^25,26

The aim of the pilot study described in this paper was to highlight techniques used by a trained expert sharp-weapon user (n = 3 knives) and to evaluate severance appearance. It is acknowledged that this pilot study has limitations with respect to number of participants and knives used, but the resulting textile damage and how it differs compared to previously reported knife impact textile damage is important with respect to forensic textile science.

Methods

A hollow polymeric, headless, retail display male mannequin (The Shopfitting Shop Ltd, Holmes Chapel, UK) was used to create a mold (Figure 1). Select body landmarks were measured on the mannequin according to ISO 7250-1:2008²⁷ (chest circumference = 910 mm and waist circumference = 740 mm).

Figure 1.

Retail mannequin used to form the PermaGel™ mold: (a) complete mannequin; (b) front and back sections of the mannequin.

PermaGel™, which is used as a simulant for human tissue,²⁸ was used to fill the mold to create three male torsos for testing. Each PermaGel™ torso was secured to a steel frame (total torso height = 870 mm, height from torso extremity to floor = 708 mm) (Figure 2(a)).

Figure 2.

Experimental set-up: (a) uncovered PermaGel™ torso; (b) T-shirt mounted on the PermaGel™ torso.

A mass produced T-shirt was selected for this pilot study as a typical example of clothing covering the male torso (Bonds Flexits™ Raglan Tee, designed in Australia, made in China; purchased from Bonds Industries Pty. Ltd, Australia). The T-shirts were size small, 97% cotton/3% elastane, bleached white, knitted single jersey, crew neck, short raglan sleeved. The T-shirts were laundered before use according to the care instruction label. The T-shirts were then conditioned to 20℃ ± 2℃ and 65% ± 4% relative humidity (RH) in accordance with ISO 139:2005²⁹ and selected fabric properties were measured (Table 1).

Table 1.

Selected fabric physical properties

	Mass per unit (n = 5; g/m²)^a	Thickness (n = 10; mm)^b	Wales (n = 5; per cm)^c	Courses (n = 5; per cm)^c
Mean	145.5	0.548	13.0	19.0
SD	1.4	0.014	0.0	0.0

AS 2001.2.13: 1987.

AS 2001.2.15: 1989 (Procedure A: Static thickness).

AS 2001.2.6: 2001 (Test B: Determination by traversing thread counter).

The T-shirts were placed over the PermaGel™ torso with the center front of the garment in line with the center front of the torso; the bottom opening hung freely as if worn loosely (i.e. not tucked in). The impacted surface was the front of the T-shirt (Figure 2(b)).

Three different knives were selected for this study as follows:

Mantis Karambit MK-1 Cinq1 (blade length = 51 mm, maximum blade width = 25 mm);

Cold Steel® Culloden™ (blade length = 127 mm, maximum blade width = 29 mm); and

Blackhawk XSF™ Micro Plain (blade length = 81 mm, maximum blade width = 28 mm); (Figures 3(a)–(c)).

Figure 3.

Experimental knives and personal protective equipment: (a) Mantis Karambit MK-1 Cinq1; (b) Cold Steel® Culloden™; (c) Blackhawk XSF™ Micro Plain; (d) Niroflex chainmail protective glove.

The back (spine, outside edge) of the Mantis Karambit knife was not sharpened, that is, this knife had a single-edged flat parallel blade. The belly (inside edge) of the blade had a non-serrated sharpened edge, part of which was concave (approximately three-quarters), the remaining being linear. The Mantis blade was manufactured from 420HC stainless steel.

The Cold Steel® knife had a double-edged blade with one side serrated along the whole length and the other side serrated for approximately one third of the length closet to the handle. The Cold Steel® blade was manufactured from AUS-10A stainless steel.

The Blackhawk XSF™ blade is a full-tang and manufactured from AUS-8A stainless steel, which is Teflon® coated. The Blackhawk XSF™ knife also had a double-edged blade that was flat and parallel; neither edge was serrated.

These knives were selected to demonstrate the differences associated with (i) technique during an attack and (ii) effect on fabric severance appearance.

A Niroflex chainmail protective glove was used to protect the trained sharp-weapon user’s hand (Figure 3(d)).

Ethical approval for this study was granted by Cranfield University (approval number 004_2013). A male trained in the Filipino martial arts discipline of Eskrima (a martial art style originating from the Philippine Islands also known as Arnis or Kali; Eskrima is used by a number of police and military forces around the world as a basis for knife defense training)⁷ participated in this pilot study. The sharp-weapon expert was given no prior guidelines for the simulated attacks, although he did assume the target (PermaGel™ torso dressed in a T-shirt) to be right handed. One PermaGel™ torso and one T-shirt were used for each knife type (n = 3). The expert approached the target in the manner applicable to the knife used. With the knife drawn, he then carried out a simulated attack on the target using his right hand, which was protected by a chainmail glove. High-speed video was used to record each trial with one camera positioned to record the hand action and impact location and the other positioned behind the participant to identify the participant’s overall body movement.

While still mounted on the torso, each severed T-shirt was immediately photographed following the impact trial using a Canon EOS 60D digital camera fitted with a Canon EFS 17 - 85 mm lens. The T-shirts were then carefully removed from the torso and laid flat under no tension with side and sleeve seams aligned. Fabric severances and surrounding features were examined under magnification up to 40× using a Motic Trinocular Zoom SMZ-143 N2GG stereo-microscope equipped with a Moticam 480 camera linked to Motic Image Plus, version 2.0 capture software (Australian Instrument Services Pty. Ltd, Australia). Fabric severance length (>1 mm) was measured to the nearest millimeter at a minimum of 4 hours after removal of the T-shirt from the torso. This was to simulate a delayed forensic examination during a textile damage investigation, which might affect severance dimensions and appearance. High-speed video was then analyzed to determine the mode and sequence of impact.

Results

Damage to T-shirts

Photographs of severed T-shirts while mounted on the torso are presented in Figures 4 and 5; severance lengths are provided in Table 2. Damage was affected by the weapon used; thus, the results are presented for each weapon individually.

Figure 4.

T-shirt severances created by each knife while mounted on the torso: (a) Mantis Karambit MK-1 Cinq1; (b) Cold Steel® Culloden™; (c) Blackhawk XSF™ Micro Plain.

Figure 5.

Additional views of T-shirt severances created by each knife while mounted on the torso: (a) Mantis Karambit MK-1 Cinq1; (b) and (c) Cold Steel® Culloden™; (d) Blackhawk XSF™ Micro Plain.

Table 2.

Summary of severance properties

		Severance length (mm)
Knife	Number of severances (n)	Minimum	Maximum	Total attack time (s)
Mantis Karambit MK-1 Cinq1	17	2	263	3.907
Cold Steel® Culloden™	23	1	282	3.905
Blackhawk XSF™ Micro Plain	34	1	44	5.368

Mantis Karambit MK-1 Cinq1

The T-shirt severed with the Mantis Karambit knife showed a distinctive slashing technique compared to the other knives considered; the blade had been used to slash the T-shirt diagonally predominantly in the upper left chest region (Figure 4(a)). Two of these slashes were over the T-shirt sleeve seam; one fully cut the seam. Slashes made over to the sleeves were perpendicular to the wales due to the garment’s construction. The blade tip was also used to create smaller isolated penetrating holes in the T-shirt fabric (n = 9) (Figure 5(a), examples are circled). Seventeen severances were identified that measured between 2 and 263 mm in length; the total attack time was <4 s (Table 2).

Cold Steel® Culloden™

The T-shirt severed with a Cold Steel® knife (Figure 4(b)) was primarily slashed, with one isolated hole. A large impact was made to the lower left of the torso (circled in Figure 4(b)) where the T-shirt fabric was drawn into the simulant and remained after knife withdrawal. The torso’s left underarm was also a target (Figure 5(b)). This particular knife was serrated and some of the severances had a distinctive ragged edged appearance. However, the severance created perpendicular to the wales along the chest center of the torso did not show the same ragged edge characteristics (Figures 4(b) and 5(c)). One severance created parallel to wales (length of T-shirt) was adjacent to a previously created severance. Twenty-three severances were identified that measured between 1 and 282 mm in length; the total attack time was <4 s (Table 2).

Blackhawk XSF™ Micro Plain

The T-shirts severed with the Blackhawk XSF™ knife (Figure 4(c)) showed isolated puncture holes. Some areas of fabric were targeted but not perforated (circled in Figure 5(d)) and, in one instance, the fabric remained in the simulant after knife withdrawal. Severances that were longer in length than the blade width were created either perpendicular or horizontal in relation to fabric wales (length of T-shirt). Thirty-four severances were identified that measured between 2 and 44 mm in length; total attack time was <5.5 s (Table 2).

Typical microscopic images of severances are presented in Figure 6. All knives were used as stabbing and slashing instruments.

Figure 6.

Typical microscopic images of severances (magnification 15×). Typical stab impact: (a) Mantis Karambit MK-1 Cinq1; (b) Cold Steel® Culloden™; (c) Blackhawk XSF™ Micro Plain. Typical slash impact: (d) Mantis Karambit MK-1 Cinq1; (e) Cold Steel® Culloden™; (f) Blackhawk XSF™ Micro Plain.

Figures 6(a)–(c) show typical severances formed when the knives were used to perforate the fabric using a stab motion. The main observations from stab severances were that (i) the Mantis Karambit knife appeared to cut the yarns with relatively little displacement (Figure 6(a)), (ii) the Cold Steel® knife created a jagged severance with multiple unraveled yarns (Figure 6(b)) and (iii) the Blackhawk XSF™ knife produced severances with few severed yarns (Figure 6(c)), which were often not visible when viewed macroscopically. The direction of the blade could be determined in some stab impacts created by the Mantis Karambit and Cold Steel® knives. It was not possible to distinguish the direction of severances created with the Blackhawk XSF™ knife.

Figures 6(d)–(f) show typical severance edges created using a slash technique. The main observation of slash severances were as follows.

The Mantis Karambit severance edges had a ‘stepping’ pattern (Figure 6(d)).

The Cold Steel® knife created severance with jagged edges and multiple areas of significant yarn unraveling, a trait more commonly seen when the wales were severed diagonally (Figure 6(e)).

The Blackhawk XSF™ knife produced a variety of characteristics. Either damage was created to the fabric surface partially severing yarns or, for larger slash cuts, the yarns had fibrillated ends that could be interpreted as being more similar to a tear than a cut.

Analysis of high-speed video

High-speed video provided supplementary information to the macroscopic and microscopic evaluations of severance damage. Firstly, once the T-shirt was perforated, the participant occasionally pushed the knife to further penetrate the simulant by leveraging power from his body position or an assisted push from his left hand (i.e. the hand not holding the knife). Secondly, the knife withdrawal did not always follow the same plane as the knife impact, which created further fabric damage.

When the fabric was severed using a slash technique two characteristics were observed:

the slash was inflicted by directly dragging the knife blade along the fabric surface; or

the slash was initiated after an initial stab penetration, creating severances with a varied axis.

Several attempts were made to slash the T-shirt covered torso with little or no damage, particularly when using the Mantis Karambit and Blackhawk XSF™ knives.

The sequence and direction in which the participant orientated his attack were plotted for the Mantis Karambit (Figure 7). Due to the technique of the simulated attacks, it was not possible to precisely plot the attack sequence for the Cold Steel® and Blackhawk XSF™ knives.

Figure 7.

Impact sequence and direction of impact in relation to the Mantis Karambit MK-1 Cinq1.

The number of impact strikes attempted by the participant per second on the torso was determined from high-speed video (Table 3). The greatest number and fastest strikes were noted for the Mantis Karambit knife; the number of strikes for the other two knives was similar, but the strikes made with the Blackhawk XSF™ knife were slower.

Table 3.

Summary of recorded attack strikes versus time

		Number of strikes recorded
Knife	Recorded attack time (s)	Total	Per second
Mantis Karambit MK-1 Cinq1	3.907	12	3.1
Cold Steel Culloden™	3.905	7	1.8
Blackhawk XSF™ Micro Plain	5.368	8	1.5

Discussion

Two aspects to this pilot study require further discussion: (i) the experimental procedure and (ii) the severance evaluation.

Experimental procedure

Particular emphasis should be placed on laboratory simulation practices when recreating physical textile damage caused by knives. In this study a static male torso surrogate manufactured from a tissue simulant was used, but limitations were present with this experimental approach. For instance, during a violent attack, the victim’s movement will play a role in the attack method of both skilled and unskilled attackers. In particular, the defensive use of the limbs (i.e. arms and legs) and stance become important. A trained user will use the victim’s arms to reposition them to open up space for cuts, or the victim may be quickly left vulnerable by having their arms (their first line of defense) neutralized by cuts. The knives used in this study had different handles, which determined how the trained sharp-weapon user gripped the handle and used the weapon. Observations regarding the influence of knife handle design during human performance have previously been reported.³⁰

The severance evidence presented in this pilot study highlighted the different appearance of damage created by a trained user with different knives; this is useful information for textile add damage before examiners. A victim with multiple sharp force wounds could have been attacked by more than one weapon or perpetrator or, as in this pilot study, a single perpetrator with a single knife. The scenario might be difficult for a pathologist to determine, particularly if no weapons are recovered. As this pilot study has shown, it is possible to inflict varied fabric severance with a single assailant using one knife.

Severance evaluation

All three knives used in this study were used to create severances that were either diagonal or perpendicular to the wale direction of the fabric. Few severances were created parallel to the wales (isolated punctures were categorized separately due to their circular shape). A similarity between previous work and this current pilot study was the angle of impact with which the participant chooses to strike the target.²⁰ It appeared that trained sharp-weapon users were more likely to impact the target on a varied angle, and remove the weapon on a different angle or twist the knife during withdrawal, easing the release of the knife and increasing wounding to the target.

The severance appearance was different when photographed while on the torso in comparison to when removed and laid flat in the laboratory. This was possibly due to a number of reasons, including the following:

tension placed on the fabric;

support from the underlying tissue simulant;

drape of the fabric as it was vertically mounted;

repositioning of the garment during the simulated attack, causing fabric folds; and

presence of fabric remaining in the tissue simulant.

By carefully laying the severed T-shirts flat under no tension and aligning the garment seams, the examination was consistent among all three T-shirts. However, matching the severances to the attack sequence proved to be more difficult with different blades, particularly on the T-shirt severed with the Cold Steel® knife, where more than one slash in a similar area resulted in overlapping severances.

Single jersey fabrics are considered to be an unstable structure, which results in curling of severed edges. Curling has been acknowledged to be associated with severed single jersey fabrics. In this study, curling was observed as follows:

when severed perpendicular to the wales, the severed edges curled towards the technical front of the fabric; and

when severed parallel to the wales, the severed edges curled to the technical back of the fabric.

Conclusions

This pilot study demonstrated variability in severances associated with an attack from an expert sharp-weapon user. This variability occurred (1) within a single attack due to variation of the technique used and (2) among attacks using different knives. It is possible that a textile examiner presented with damaged clothing similar to that created in this pilot study would find it difficult to draw firm conclusions from it, and might conclude the attack was due to several perpetrators with different weapons. The pilot study presented in this paper reinforces the variability of severances that can be created in a clothing layer during a knife attack.²⁰

The conclusions drawn from this pilot study are limited by the use of a single expert user and the three knives used, but the work does raise important issues for the forensic textile science community concerned with textile damage to consider.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: EJC acknowledges receipt of a Cranfield University Visiting Research Studentship and a Research Training Scheme (RTS) PhD Tuition Scholarship at RMIT University.

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