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| An '''abrasion collar''', also known as an '''abrasion ring''' or '''abrasion rim''', is a narrow ring of stretched, abraded [[skin]] immediately surrounding projectile wounds, such as [[Gunshot wound|gunshot wounds]]. It is most commonly associated with [[entrance wound|entrance wounds]] and is a mechanical defect due to a projectile's penetration through the skin. It is caused by a temporary over-stretching of the skin surrounding the projectile's point of penetration. Like all skin abrasions, the abrasion collar tends to dry out due to scraping away of the skin's outer layers and the collapse and dehydration of the underlying cells; it therefore becomes easier to discern with time.<ref name="forensicmed">{{cite web |title=Gunshot wounds - rifled weapons |url=http://www.forensicmed.co.uk/wounds/firearms/gunshot-wounds-rifled-weapons/ |website=Forensic Medicine for Medical Students |accessdate=9 June 2019 |ref=forensicmed |archive-url=https://web.archive.org/web/20181211070957/http://www.forensicmed.co.uk/wounds/firearms/gunshot-wounds-rifled-weapons |archive-date=11 December 2018 |url-status=live }}</ref> This defect is most often seen around [[rifling|rifled]] [[firearm]] entrance wounds due to the [[wikt:striation|striation]]s or grooves in the [[bullet|bullet's]] surface caused by the rifling on the inside of the weapon's [[Gun barrel|barrel]]; however, certain other high-velocity projectile wounds can also have the same effect.<ref name="Ajay">{{cite journal|last1=Gujaral|first1=PB|last2=Ajay|first2=B|title=Abrasion Collar Around Shrapnel Entry Wound.|journal=J Forensic Sci|volume=62|issue=6|pages=1635–1637|date=28 February 2017|doi=10.1111/1556-4029.13457|pmid=28244192|url=https://www.ncbi.nlm.nih.gov/pubmed/?term=abrasion+collar+around+shrapnel+entry+wound|accessdate=29 June 2017|archive-url=https://web.archive.org/web/20180724010249/https://www.ncbi.nlm.nih.gov/pubmed/?term=abrasion+collar+around+shrapnel+entry+wound|archive-date=24 July 2018|url-status=live}}</ref>
| | {{Short description|A feature of gunshot wounds}} |
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| An abrasion collar is usually found in association with a ''[[contusion]] collar'' of [[Bruise|bruising]] caused by damaged [[Blood vessel|blood vessels]] in the skin by [[hydrostatics|hydrostatic]] forces from the bullet's entry.<ref name="dineshrao">{{cite web |last1=Rao |first1=Dinesh |title=Firearm injuries |url=http://forensicpathologyonline.com/E-Book/injuries/firearm-injuries |website=Dr Dinesh Rao's Forensic Pathology |accessdate=10 June 2019 |ref=dineshrao |archive-url=https://web.archive.org/web/20190319143054/http://www.forensicpathologyonline.com/E-Book/injuries/firearm-injuries |archive-date=19 March 2019 |url-status=live }}</ref> An abrasion rim defect is also possible in firearm [[exit wound]]s under certain circumstances, such as if the skin at the exit was crushed between the outgoing [[bullet]] and an unyielding object pressed against the skin over the exit site, or if the projectile exits at an extreme angle. Careful examination of the wound under magnification may show signs of everted (outward-turned) edges characteristic of an exit wound.<ref name="Shored">{{cite journal|last1=Aguilar|first1=JC|title=Shored gunshot wound of exit. A phenomenon with identity crisis.|journal=Am J Forensic Med Pathol|date=September 1983 |volume=4|issue=3|pages=199–204|pmid=6637946|doi=10.1097/00000433-198309000-00003}}</ref> Multiple projectiles impacting in close proximity together, such as in a close-range [[shotgun]] blast, will usually still produce an abrasion rim or artefact, though the wound will likely be irregular in shape.<ref name="dineshrao"></ref>
| | '''Abrasion collar''' is a term used in forensic pathology to describe a specific type of injury pattern associated with [[gunshot wounds]]. It is a crucial feature that helps forensic experts determine the characteristics of the wound and the direction of the projectile. |
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| == Factors and characteristics == | | ==Description== |
| | An abrasion collar, also known as a "marginal abrasion," is a ring of abraded skin that surrounds the entrance wound of a bullet. This abrasion occurs as the bullet penetrates the skin, causing the outer layers to scrape against the projectile. The presence and characteristics of an abrasion collar can provide valuable information about the angle and direction of the bullet's entry. |
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| === Bullet wipe === | | ===Characteristics=== |
| In the case of [[gunshot wound|gunshot wounds]] from unjacketed [[lead]] alloy bullets or dirty bullets, a phenomenon known as ''[[bullet wipe]]'' may be observed, which forms a ring of greasy residue known as a ''grease'' or ''dirt collar'' that overlays the abrasion collar and is caused by deposits on the skin's surface. Generally, these deposits contain lead from the unjacketed projectile or oil from inside the weapon's barrel, but they may simply be dirty. Studies using [[high-speed photography]] have shown that bullet wipe is caused only by the head of the bullet—instead of the body—because the skin recoils away from the bullet as it penetrates due to the force of entry.<ref name="forensicmed" />
| | The abrasion collar is typically characterized by: |
| | * '''Color''': The collar often appears as a reddish-brown ring around the entrance wound. |
| | * '''Width''': The width of the abrasion collar can vary depending on the angle of entry and the type of projectile. |
| | * '''Shape''': The shape of the collar can indicate the angle of the bullet's entry. A circular collar suggests a perpendicular entry, while an oval or irregular shape may indicate an angled entry. |
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| === Angle of trajectory === | | ==Forensic Significance== |
| The bullet's angle of [[trajectory]] at the point where it penetrates the skin can influence the shape of the abrasion collar. This can be used by [[forensic pathologist|forensic pathologists]] in discerning an approximate angle of entry and is important in investigations of gunshot wound victims, where evidence of the gunshot's origin is necessary to determine whether the death was [[homicide|homicidal]], [[suicide|suicidal]], or accidental. Generally, if the bullet impacts at an angle [[perpendicular]] to the skin surface, the abrasion collar will be symmetrical, concentric, round, and evenly-shaped. As the angle between the trajectory and the skin surface decreases, the abrasion collar becomes more distorted and often more distinct at the point of entry, having a semi-lunar or "half-moon" shape with the broadest width pointing in the direction of the gunshot's origin.<ref name="dineshrao"/> This is caused by the exterior of the bullet contacting and scraping over the skin's surface for a certain distance before penetrating the skin.<ref name="forensicmed"></ref> | | The analysis of an abrasion collar is an important aspect of forensic investigations involving [[firearm injuries]]. It can help determine: |
| | * '''Direction of Fire''': By examining the shape and distribution of the abrasion collar, forensic experts can infer the direction from which the bullet was fired. |
| | * '''Range of Fire''': The presence of additional features, such as [[gunpowder tattooing]] or [[stippling]], in conjunction with the abrasion collar, can help estimate the range of fire. |
| | * '''Type of Weapon''': The characteristics of the abrasion collar, along with other wound features, can assist in identifying the type of firearm used. |
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| === Bullet shape and velocity === | | ==Related Pages== |
| The bullet shape influences the size of the abrasion collar.<ref name="Shape">{{cite journal|last1=Pircher|first1=R|last2=Pollak|first2=S|last3=Preiß|first3=D|last4=Thierauf-Emberger|first4=A|last5=Perdekamp|first5=MG|last6=Geisenberger|first6=D|date=March 2017|title=The influence of the bullet shape on the width of abrasion collars and the size of gunshot entrance holes.|journal=Int J Legal Med|volume=131|issue=2|pages=441–445|doi=10.1007/s00414-016-1501-6|pmid=27909866}}</ref> High velocity bullets with pointed, narrow, or [[spitzer bullet|spitzer]] tips, such as rifle rounds, and [[full metal jacket bullet|full metal jacket bullets]] are less likely to produce abrasion collars compared to lower-velocity, [[semi-jacketed bullet|semi-jacketed]] civilian bullets, such as bullets fired from [[handgun|handguns]], which have rounded noses.<ref name="Thai">{{cite journal|last1=Peonim|first1=V|last2=Srisont|first2=S|last3=Udnoon|first3=J|last4=Wongwichai|first4=S|last5=Thapon|first5=A|last6=Worasuwannarak|first6=W|date=November 2016|title=Entrance and exit wounds of high velocity bullet: An autopsy analysis in the event of dispersing the mass rally in Bangkok Thailand, May 2010.|journal=Leg Med (Tokyo).|volume=23|pages=10–16|doi=10.1016/j.legalmed.2016.08.010|pmid=27890096}}</ref>
| | * [[Gunshot wound]] |
| | * [[Forensic pathology]] |
| | * [[Ballistics]] |
| | * [[Stippling]] |
| | * [[Gunpowder tattooing]] |
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| If the wound is caused by a high-velocity rifle bullet, the abrasion collar may be smaller, but it may have minute tears in the surface of the skin surrounding the wound entrance. This is because the skin is not capable of stretching quickly enough if the bullet's velocity is too high. If the wound is made over [[bone]], such as a head wound in the [[scalp]], the abrasion collar may not be round at all; it instead becomes stellate or "star-shaped" with ragged and torn edges caused by the skin over-stretching and tearing. In the case of [[skull]] entrance wounds, the skin that includes the abrasion collar may be torn away because the underlying tissue is unable to flex away from the force of the bullet's entry.<ref name="forensicmed" />
| | [[Category:Forensic pathology]] |
| | | [[Category:Gunshot wounds]] |
| === Wound distortions ===
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| Towards the end of a bullet's [[ranged weapon|effective range]], it tends to lose [[Rotation around a fixed axis|axial stability]] and will begin to [[yaw (rotation)|yaw]] or even tumble end-over-end. This means it may impact the skin while travelling sideways, and the resulting wound may be distorted, irregular in shape, or even slit-like, such that it does not resemble a conventional entrance wound. In this case, an abrasion artefact may be absent.<ref name="dineshrao"/> Similarly misshapen wounds can be caused by the distortion of the bullet if it hits an intermediate object (including another part of the victim's own body, in what is known as a ''re-entrant wound'') before penetrating the skin surface. However, careful examination of the wound under magnification may show the inverted wound edges and signs of an irregularly-shaped abrasion rim characteristic of entry wounds.<ref name="forensicmed"/>
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| ==References==
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| {{reflist}}
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| [[Category:Medical terminology]] | |
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A feature of gunshot wounds
Abrasion collar is a term used in forensic pathology to describe a specific type of injury pattern associated with gunshot wounds. It is a crucial feature that helps forensic experts determine the characteristics of the wound and the direction of the projectile.
Description[edit]
An abrasion collar, also known as a "marginal abrasion," is a ring of abraded skin that surrounds the entrance wound of a bullet. This abrasion occurs as the bullet penetrates the skin, causing the outer layers to scrape against the projectile. The presence and characteristics of an abrasion collar can provide valuable information about the angle and direction of the bullet's entry.
Characteristics[edit]
The abrasion collar is typically characterized by:
- Color: The collar often appears as a reddish-brown ring around the entrance wound.
- Width: The width of the abrasion collar can vary depending on the angle of entry and the type of projectile.
- Shape: The shape of the collar can indicate the angle of the bullet's entry. A circular collar suggests a perpendicular entry, while an oval or irregular shape may indicate an angled entry.
Forensic Significance[edit]
The analysis of an abrasion collar is an important aspect of forensic investigations involving firearm injuries. It can help determine:
- Direction of Fire: By examining the shape and distribution of the abrasion collar, forensic experts can infer the direction from which the bullet was fired.
- Range of Fire: The presence of additional features, such as gunpowder tattooing or stippling, in conjunction with the abrasion collar, can help estimate the range of fire.
- Type of Weapon: The characteristics of the abrasion collar, along with other wound features, can assist in identifying the type of firearm used.
Related Pages[edit]
