Abrasion

1.Scratch abrasion

• Synonym: linear abrasion
• Sharp or pointed object not sharp enough to cause incised wound, but pointed enough to scratch
• E.g. thorn, fingernails(Crescent shaped abrasion ), tip of knife
• Clean area at the start of the wound and tags at the end
• Helps in determining the direction of force

2.Graze abrasion

• Synonyms: grinding or sliding abrasions, brush burns
• Most common type – Commonly seen in road traffic accidents
• Mimics burn
• Occurs when the skin is rubbed (friction) against some rough surface
• Uneven, longitudinal parallel lines of abrasion are seen
• Epithelium heaped up at the end of these lines which indicates the direction of force

3. Pressure abrasion

• Synonym: crushing abrasion
• Sustained pressure of a rough object at 90° – crushing of the superficial layers of the skin
• No force on impact, but sustained pressure after the object comes in contact with body surface
• E.g. Ligature mark in hanging and strangulation

4. Impact abrasions

• Synonym: Contact abrasion or Imprint abrasion
• There is a moment of forceful impact, after that no contact of the object with body
• E.g: radiator grill mark, tyre tread marks seen in RTA 

 Artifacts in Abrasion 

• By Ants.
• By Insects.
• By Animals.
• By Marine animals. 

Medico legal importance

• Gives a clue about the direction of trauma 

• Helps to identify certain features of the causative agent 

Imprint of the muzzle of a shotgun (Abrasion ring)

Imprint of the hilt guard of a knife

• Helps in finding the time of injury  
• The pattern of abrasions provide evidence of the nature and the mechanism of trauma. 
• eg. grazed abrasions in different directions all over exposed areas of the body indicate that a body has been thrown on a rough surface in different directions.
• An abrasion can be categorized for medico legal purposes .  
• Helps in reconstructing the incident  eg. finger nail abrasions in strangulation helps in finding the relative position of both victim and the assailant
• Indicates the type of crime  eg. strangulation, sexual offence etc