FSC 451 Chapter 7 (Wounds Caused by Pointed and Sharp-Edged Weapons)

What are the four categories of wounds caused by pointed and sharp-edged weapons?

1. Stab wounds

2. Incised wounds (cuts)

3. Chop wounds

4. Therapeutic/ diagnostic wounds

What defines a stab wound?

• produced by pointed instruments

• depth of wound track exceeds skin length

• skin edges are sharp and clean

• No abrasion or contusion at margins

• do NOT call a stab wound a laceration (Lacerations = blunt force)

What weapons commonly cause stab wounds?

• Most common: knife

-flat bladed, single-edged

-kitchen, pocket, or folding knifes

• other objects

-ice picks

-scissors

-screwdrivers

-broken glass

pens, pencils, forks

Does a deep stab wound mean great force was used?

• not necessarily

• force depends on:

-Sharpness and configuration of the tip

• Sharp, needle-like tips penetrate skin easily

• Once skin is penetrated, the blade slides through soft tissue with little force

• Full blade insertion does not equal high force unless bone is contacted

How does skin elasticity affect stab wound length

• Skin wound length can be

-equal to

-less than

-greater than blade width

• Factors:

-skin elasticity/laxity

-blade slicing against skin

• measurements may differ by 1-2 mm from actual blade dimensions

How does stab wound depth relate to blade length

• depth can be:

-less than blade length

-equal to blade length

-greater than blade length

• greater depth occurs when

-body wall is compressed (abdomen, chest)

• Multiple wounds allow estimation of blade size

What is the importance of skin-to-organ distances?

• CT studies show minimum distances from skin to organs

• No significant differences between sexes

• Measurements may overestimate real-life penetration due to tissue compression

• Used to assess potential lethality of wound depth

What determines the appearance of a stab wound?

• blade shape and sharpness

• direction of thrust

• movement of the blade in the wound

• movement of the victim

• skin tension vs relaxation

• angle of entry

How does blade sharpness affect wound margins?

• Sharp blade → clean, regular edges

• Dull blade → abraded, bruised, or jagged edges

• Oblique entry→ beveled margin on one side, undermining the other

• beveling indicated direction of entry

What are the parts of a single- edged knife?

• grip

• guard (crossguard)

• Ricasso

• Back (spine)

• Edge

• Point

What is a guard mark and when does it occur?

• Patterned abrasion caused by guard contacting skin

• Occurs when knife is plunged to full blade length

• Guard mark location indicated direction:

• Downward thrust→ mark above wound

• Upward thrust → mark below wound

• Oblique thrust → mark on one side

• Term “hilt” is incorrect for knives

How do langers lines affect stab wound shape?

• perpindicular to lines → gaping wounds

• Parallel to lines → narrow, slit-like wounds

• oblique→ asymmetric or semicircular wounds

• approximating wound edges gives the best estimate of maximum blade width

How do stab wound differ between single and double-edged knives?

• double edges:

-Both ends pointed

• single-edged:

-One pointed end

-one squared or blunted end

• BUT:

-Single-edged knives often produce bilateral pointed wounds

• due to:

-Cutting edge near tip on spine

-knife motion during withdrawal

What causes Y or L-shaped stab wounds?

• Knife twisting during withdrawal

• movement of the victim

• primary stab + secondary cutting path

• Common in forensic misinterpretation → twisting vs movement

What causes a “forked” end on a stab wound?

• partial rotation of the knife

• Cutting edge creates an inverted V-shaped notch

• one end blunt/squared, the other forked

• can mimic taring from ricasso

How do ricasso tears differ from sharp cuts?

• caused by an unsharpened ricasso

• superficial

• not clean or sharp

• confined to upper skin layers

• can mimic forked wounds

What are features of ice pick stab wounds?

• small, round, or slit-like

• easily missed

• may resemble:

-Shotgun pellet wounds

-.22-caliber bullet wounds

• minimal external bleeding

What do fork stab wounds look like?

• clusters of 2-4 wounds

• equally spaces

• match number of prongs

• kitchen forks usually cause superficial injuries

• fatalties extremely rare

What characterized screwdriver stab wounds?

• Philips head:

-X-shaped or circular wound

-Four equally spaced cuts

• flat head:

-Slit-like wound

-squared ends

-abraded margins

• often difficult to distinguish from narrow knifes

Can pens and pencils cause fatal stab wounds?

yes

• neck penetration

• spinal cord injury

• fatal outcomes

• often underestimated in lethality

How do scissor stab wounds appear?

• closed scissors

-splitting injury

-linear wound with abraded margins

• open scissors:

-two separate stab wounds

-A protruding screw can cause angular laceration

What are features of broken bottle stab wounds?

• clustered wounds

• variable size, shape,and depth

• Sharp but ragged edges

• Most fatal causes are homicides

• rare accidents and suicides reported

Why is weapon identification from a single stab wound unreliable?

• wound shape influenced by:

-skin elasticity

-movement

-angle

-withdrawal motion

• multiple wound needed to infer blade characteristics

• Never identify weapon type from one wound alone

Identifying the weapon from a stab wound

• pathologists must be extremely cautious when identifying weapons

• most reliable information from a wound:

-Maximum blade width

-approximate blade length

-single vs. double edged

• serrations are rarely identifiable from wound appearance

• angle of entry matters:

-oblique wounds distort edges

-this match is considered as strong as a ballistics match

Blood & DNA evidence on knives

• Knives may show no visible blood even if used in a stabbing

• reasons:

-Pressure of the knife prevents bleeding with in situ

-tissue contraction wipes the blade during withdrawal

-Clothing may wipe the blade clean

• Important exam areas:

-Blade

-Handle

-Recess of folding knives

• Even clean looking knives may yield DNA from blade wipings

Removal of a knife embedded in the body

• grasp sides of the handle near the skin

• avoid touching areas handled by the assailant

• purpose: preserve fingerprints and trace evidence

Cadaveric Spasm and weapon presence

• A weapon firmly clenched in the hand may indicate cadaveric spasm

• occurs at the moment of death

• provides strong evidence victim held weapon before death

Stab wounds-Manner of death patterns

• Most stab wounds are homicides

• Homicide:

-Multiple wounds

-widely scattered

-Many are not deeply penetrating

• suicide:

-uncommon

-often mild or left chest

-multiple shallow “hesitation wounds.”

-usually 1-2 fatal penetrating wounds

Seppuku (hara-kiri)- forensic characteristics

• rare, ritual suicide

• Single large abdominal wound

• Knife drawn:

-Across the abdomen

-Then upward→ L-shaped incision

• rapid death due to:

-Sudden loss of intra-absominal pressure

-Cardiac collapse

Impaling injuries-key features

• Very uncommon

• Most often accidental:

-falls

-Traffic accidents

• examples:

-Fences, pipes, metal rods

-Vehicle cargo shifting forward

• rare intenional impalement (often sexual, anal/genital)

Most fatal stab wound location

• Left chest

• Reasons:

-Most people are right-handed

-Heart located on the left

• frequently involves:

-Heart

-aorta

-lung

Cardiac Tamponade in stab wounds

• occurs when >150 mL of blood accumulates in the pericardial sac

• Death can occur at any time

• Usually combined with:

-Hemopericardium

-hemothorax

-external blood loss

Ventricles vs atria - Severity in stab wounds

• Atrial or great vessel injuries are most serious

• ventricular muscle contracts → may slow bleeding

• severing the LAD coronary artery is rapidly fatal

Lung stab wounds - cause of death

• usually die from:

-Exsanguination

-massive hemothorax

• pneumothorax may also occur

Abdominal stab wounds - lethality

• fatal injuries often involve

-liver

-major vessels (aorta, vena cava, mesenteric)

• Bowel injuries → Delayed death from peritonitis

• only ~2/3 penetrate abdominal cavity

• <50% cause major visceral injury

Stab wounds of head & neck

• neck:

-Rapid death from hemorrhage, air embolism, or asphyxia

-trachea and vessels may be severed

• head and brain:

-uncommon

-often through eye or temporal bone

-victim may initially remain mobile

Stab wounds of the brain- key points

• knife blade may remain embedded

• injury may go unnoticed initially

• death due to:

-intracranial hemorrhage

-infection

• skull defect matches:

-blade width/thickness

-or ice pick diameter

Spine stab wounds

• rare

• knife blade may break off in the spine

• Causes:

-partial or complete paralysis below injury

• delayed presentation possible (years later)

Ice pick stab wounds

• small, inconspicuous external wound

• minimal external bleeding

• can penetrate deeply and be missed at a scene

• often fatal due to vascular injury

Probing stab wounds- why its discouraged

• produces false wound tracks

• alters original injury

• provides little useful information

• not recommended

Incised- stab wound

• begins as stab wound

• knife is then drawn outward

• converts to a slash-type incision

• length of wound increases due to blade movement

Physical activity after a fatal stab wound

• depends on

-organ injured

-blood loss

-rate of bleeding

• victims may:

-walk or run briefly

-leave blood trails

• fatal does not mean immediate incapacitation

What is an incised wound?

An incised wound is a cut produced by a sharp-edged instrument (e.g., knife, eazor, glass, metal, paper) where the length of the wound is greater than its depth.

How are incised wounds produced on the skin?

By a sharp edge pressed into the skin ad drawn along the surface creating clean margins.

How do incised wounds differ from lacerations?

• Incised woulds: clean, sharp edges, no abrasion or tissue bridging

• Lacerations: blunt force injuries with ragged edges, abrasions, and tissue bridging

Can the length of an incised wound determine weapon size?

NO. A short wound may be caused by a long blade and vice versa.

What does “no bridging” mean in incised wounds?

There are no intact strands of tissue crossing the wound depth (unlike lacerations)

Can the exact force used to inflict a fatal stab wound be determined?

No, but force can be estimated comparatively based on several variables.

What weapon characteristics affect force required for penetration?

• sharp vs. dull point

• Think vs thick blade

• Single vs. double-edged blade: Sharp, thin, double-edged blades require less force

How does tissue type affect penetration force?

• Skin, cartilage, bone → require more force

• Fat and muscle → require less force

How does wound depth relate to force?

• greater depth (e.g., a 4-inch deep wound generally requires greater force.

How does clothing affect stab force?

Thick or layered clothing (leather, coats) increasing required force compared to thin clothing.

Average force needed to penetrate skin, fat, and muscle?

~11.1 Ib (49.5 N) (Range 7.9-12.4Ib)

Is bleeding from postmortem incised or stab wounds usually heavy?

No, it is usually minimal due to lack of circulation

What can postmortem bleeding be significant?

A large vessel is severed and located in a dependant area of the body

Approximate blood loss into body cavities post mortem?

300-500 mL per cavity, which is small compared to antemortem hemorrhage

Why might a stab wound appear bloodless?

Heavy bleeding from earlier wounds may deplete circulating blood before the final wound.

How can postmortem movement affect bloodstains?

Blood may escape wounds during transport, altering or enlarging stains on clothing

How do incised would edges typically appear?

They gap open, depending on orientation to skin tension lines (langer’s lines).

Incised wounds parallel to Langer’s lines do what?

Gap less than woulds made perpendicular or oblique to the lines

Are incised wounds usually fatal?

No, most are treated in emergency settings and heal with thin linear scars

Most common body locations for incised wounds?

Head, neck, and arms

What is a “wrinkle wound”?

Multiple incised cuts are caused when the skin is not flat, and the blade skips crest-to-crest.

What causes a beveled or undermined edge?

Blade held at an oblique angle to the skin.

What are hesitation marks?

Superficial, multiple incised wounds adjacent to a fatal wound, incising indecision.

Where are hesitation marks most commonly found?

Neck, wrists, forearms

Typical pattern of suicidal incised wounds?

• accessible body areas

• hesitation marks present

• often shallow initially, deeper later

Dominant-hand pattern in self-inflicted wounds?

• Right-handed → left wrist/forearm

• Left-handed → right wrist/forearm

Why are wrist cuts often non-fatal?

Victims may lack anatomical knowledge and do not sever major vessels or cut deep enough

What are defense wounds?

Injuries sustained while warding off an attack with a sharp weapon

Common locations of defense wounds?

• palms

• Backs of forearms

• Ulnar aspect of forearms

• rarely on feet or legs

Causes of incised neck wounds?

Accidental, suicidal, or homicidal

Accidental incised neck wounds are usually caused by what?

Glass injuries

Typical homicidal neck wound from behind?

• head pulled back

• knife drawn across neck

• begins high, goes downward and medically ends lower

How does handedness affect neck wound direction?

Right-handed → left-to-right

Left-handed -? right to left

Neck wounds from the front tend to look how?

Shorter, angled, slash-type wounds rather than one continuous cut

Can incised neck wounds cause death without exsanguination?

Yes, via air embolism if venous system is breached

Why are chest X-rays recommended in neck incised wounds?

To detect air embolism in the heart or venous system

Can glass be used as a weapon?

Yes, in both homicide and suicide, often caused deep incised wounds

Why are scalp wounds sometimes confusing?

Sharp objects can cause lacerations with clean edges, mimicking incised wounds—bridging must be examined

How does prolonged water immersion affect stab or incised wounds?

Blood leaches out, giving wounds a postmortem appearance even inflicted antemortem

Why is hemorrhage absence unreliable in water-recovered bodies?

Prolonged immersion can remove visible blood, making antemortem injury

What should always be examined in incised or stab wounds?

Clothing, to look for defect corresponsing to wounds and rule out post-injury dressing

What is a chop wound?

A wound caused by heavy instrument with a cutting edge

Key feature in distinguishing chop wounds from simple incised wounds

Underlying bone injury

Why may chop wounds appear incised?

They combine cutting and crushing,giving both incised and lacerated features

What happens when a chopping weapon is pulled from embedded bone?

A twisting motion may fracture or break off adjacent bone

What may chopping weapons do in tangential skull wounds?

Cut off disks of bones

How do cleavers affect bone

• clean, narrow wounds

• No fractures at entry site

• fine, sharp, distinct striations microscopy

How do machetes affect bone?

Wider, less clean wounds

small bone fragments at entry

fractures in the wound bed

striations are coarser and less distinct

How do axes affect bone?

• crushing injuries

• fragmentation with fractures

• no microscopic striations

Why is microscopic bone analysis useful?

It may help distinguish weapon class (cleaver vs machete vs axe)

What injuries can boat or airplane propellers cause?

Multiple chop-like wounds

Why are propeller wounds often difficult to time?

Water immersion may eliminate hemorrhage, mimicking postmortem injury

How can antemortem propeller injuries be confirmed?

Presence of hemorrhage in surrounding soft tissue

What are therapeutic or diagnostic wounds

Wounds produced by medical personnel during treatment

Common examples of therapeutic wounds?

• thoracotomy incisions

• surgical stab wounds for chest/abdominal drains

• laparotomy incisions

• tracheostomy incisions

• cutdowns (wrists, antecubitall fossa, ankles)

Absence of bleeding in chop or incised wounds proves postmortem injury true or false?

False water immersion can remove blood from antemortem wounds