MECHANICAL INJURY

ML Classification of Injury:

MEDICAL

1.Mechanical

A)DUE TO BLUNT FORCE

Abrasion

Contusion

Laceration

Fracturew and dislocation

B)DUE TO SHARP FORCE

a)Incised wound

b) Chop wound

c)Stab wound

C.FIREARM WOUNDS

a) Firearm wound

2.Thermal

DUE TO COLD-frost bite ,immersion foot

DUE TO HEAT-burns,scald

3.Chemical corrosive acid ,corrosive alkali

4.physical- electricity .lightning,Xray.

5.explosions

LEGAL

1.SIMPLE

2.GREVIOUS

MEDICOLEGAL

1.SUICIDE

2.HOMICIDE

3.ACCIDENT

4.FABRICATED

5.DEFENCE

Contusion:

Surface injury to the skin and sub-cutaneous which leads to an effusion of blood into tissues
usually caused by blunt trauma.
Appears 1-2 hours after injury.
may take the shape of weapon eg railway tract appearance.
Children, old, obese women bruise easily.
Mongolian spot shouldn’t be confused with bruise.
Contusion may be also in the internal organs
Gravity shifting of bruise may occur in late occuring bruises

Color changes in a bruise:

1st day- red
2nd day- 3rd day -bluish
4th day- brown day(haemosiderin)
5th-6th day- green(haematoidin)
7th-12th day- yellow(bilirubin)
13th-15th day ,2 weeks – normal
Subconjunctival Hage donot undrego colour change

ML aspect of contusion:

Patterned bruise-Identification of weapon,ligature,vehicle
Degree of violence from size
Time since injury
Purpose of injury
Homicidal, suicidal, accidental .position of assylant while arms are grasped

Difference between antemortem and postmortem bruise:

Antemortem contusion

Swelling present
Color changes present
Epithelium abraded
Clotted blood in tissue present

Postmortem contusion

Not present
Not present
Not present
Not present

Difference b/n artificial and true bruise

Artificial bruise

By juice of marking nut,calotropis or plumbago
At exposed accessible site
Dark brown colour
Shape irregular
Margins well defined and regular
Itching present
Positive chemical test

True bruise

Trauma
Anywhere
Typical colour changes
Usually rounded
Not well defined,diffuse,no vesicles
Absent
negative

Patterned intradermal bruise on the forehead due to a

fall onto ribbed ceramic tiles.

Bruising of the upper arm. The pattern of these bruises

is typical of forceful gripping. Small abrasions from fingernails are

also seen.

Typical ‘railway-line’ bruises caused by a wooden rod.

Note that the centre of the parallel contusions is unmarked.

Recent bruising of the abdominal wall and scrotum due

to kicking.

Abrasion:

destruction of only superficial layer of epidermis,thickness of skin is 1.6mm.
Bleed very slightly
Heal very rapidly
Leave no scar

Types of abrasions:

Scratch or linear abrasion-has length but no significant width.eg by pin, thorn, nail etc. very sharp objects
Graze(sliding,grinding abrasion)-longitudional parallel lines. by rough surface in contact with a broader surface of skin, eg. RTA
Patterned abrasion (pressure and impact abrasions)- thumb mark in strangulation, ligature mark in hanging, wheel mark of tyre,teethbite mark.

Age of abrasion by color change: exact age cant be determined

Red color- fresh
Red scab- 12-24 hours-by dryind of blood and lymph
Reddish brown scab- 2 to 4 days
Healing from periphery- 4 to 7 days,dark brown
Complete healing- 10 to 14 days
Seperation of scab- 10 to 14 days

ML importance:

Identification of object
Direction of injury
Time since injury
Possibility of internal injury
Somtime erosion by ants look like abrasion.d/d-ants produce abrasion that are brown,irregular margin,commonly at mucocutaneous junction about eyelids,nostril,mouth,axilla,by hand lens show multiple cresent shaped,sand like bite marks

Difference

Antemortem abrasion

has Moist surface
Bleeding present
On drying scab formation,scab slightly raised
Blurred margin
Inflammation present
Intravital reaction and congestion seen

Postmortem abrasion

Dry surface
No bleeding
No scab
Sharply defined margin
Inflammation absent
Not seen

Abrasions from scraping against a rough surface

during a fall.

Extensive abrasions caused by stumbling, drunk and

naked, against furniture. The dark leathery appearance is due to

post-mortem drying of the damaged areas of skin

Incised wound:(cut,slash,slice)

Clean cut through tissues ,usually skin and subcut. By sharp edged or cutting weapon, eg. knife, sword, glass.
Edges are smooth, clean cut and everted.
Broader than the edge of weapon
Length is greater than depth and breadth.
Bleed profusely
Superficial towards the end of wound k/a tailing
Edges may be inverted in case of underlying muscle attached to skin, eg. scrotum.

ML importance:to find homicidal,accidental or suicidal

Homicidal, anywhere in the body, deep
Suicidal- multiple, superficially, usually in the left hand
Accidental- anywhere
Edges of the wound indicate: antemortem or postmortem, sharp or blunt weapon.

Difference between incised wound

Antemortem

Bleed freely and profusely
Arterial spouting present
Blood is clotted
Edges gape
Inflammation present
Serum serotonin and histamine increased

Postmortem

Very slight or no hemorrhage
Not present
Not clotted
Edges closely
Not present
Not raised

Difference between suicidal and homicidal cut-throat wounds

Suicidal

Left side of neck,passing across the throat,usually in rt handed
Level above thyroid cartilage
Multiple no ,superficial,rarely single
Edges usually ragged,due to overlapping
Hesitation cuts present
Defence wound absent
Weapon usually present
Clothes not torn or damaged
Circumstancial evidence, quite place

Homicidal wounds

Usually on both sides
On or below thyroid cartilage
Multiple .cross each other at a deep level
Sharp and clean cut,bevelling may be seen

Incised wound to the flank; it is clearly longer than it

is deep

A complex stab wound where all three injuries are

caused by a single action. The first entry is in the right breast; there

is an exit wound in the middle and a re-entry wound over the centre

of the chest.

Stab or punctured wound:

Type of incised wound whose depth is greatest in dimension.
Eg. Knife wound, dagger

Types of stab wound:

Penetrating wound- has only wound of entry
Perforating wound- has both entry and exit wound

Features of stab wound:

Aperture is usually smaller than the weapon due to elasticity of the skin
Depth is greater than breadth and length.
Very little external hemorrhage but profuse internal hemorrhage

Shape- Wedge shaped with knife, elliptical with dagger, rounded with needle, slit-like opening with screw driver,
Margins of entry wound are clean and inverted,
Margins of exit wound are small and everted
Direction determined by line joining entry and exit wounds or X-ray after radio-opaque dyes.

ML(medical legal ) importance: