gun shot wounds

contact wounds: skull

-"spectacle hemorrhages" -orbital roof fractures -"stretch" contusion

limits of elasticity are reached at muscle velocities in excess of _________ ft/sec

2700 ft/sec

wadding contusions/abrasion may be seen out to _____ feet

50 ft

high-velocity rifle bullets: cavity undulates 5-10 msec then what?

comes to rest as a permanent track

rapid expansion of cavity can do severe damage where from wound path

damage at significant distance from wound path -depending on tissue struck

primary blast injury of the GI tract

air-containing organ -hemorrhage, contusion, and perforation of colon -more common with immersion blast

in cases of splinter injuries (by fragments of explosive weapons) the entry wound is always (smaller/larger) than the corresponding exit

always larger

small arms has a what type of path of destruction?

direct path of destruction with minimal lateral extension

high-velocity rifle bullets have a maximum cavity diameter that occurs at what point?

point of maximum loss of kinetic energy -maximum yaw or fragmentation

most frequently injured tissue by blast front

primary blast injury of the ear -tympanic membrane rupture -damage to ossicles and/or cochlea

temporary stress cavity

radially flings surrounding tissue creating a cavity larger than the diameter of the bullet

"tail splash"

rearward propulsion of injured tissue -high velocity rifle bullets

shotgun injuries: entrance wound

roughly corresponds to the gauge and is of circular shape in most body regions -stellate over the bone due to the expansion of the inrushing gases with consecutive backward ballooning of the skin

small arms = ____________ temporary cavity

small temporary cavity

sharp, irregular mortar fragments typically produce what type of hemorrhage?

soft tissue hemorrhage -with cavitation of muscle and shattering of bone

high-velocity rifle bullets cause alternating positive and negative pressure in wound track which does what?

sucks foreign material and bacterial into wound track

the use of silencers strongly reduces what?

the deposition of soot and powder particles -creates a false impression of a larger range of fire

the bullet path and the volume of the cavitation remaining after the firing of the shot are proportionate to what?

the energy transferred

"muzzle abrasion"

the entrance region is bloated by the inrushing powder gases and balloons backward against the muzzle end of the weapon, which is imprinted on the skin

autopsy procedures in explosion deaths

-take x-rays -preserve clothing -swabs for explosive residues: areas of blast injury, hands -document injury patterns -collection of trace evidence: fingernail scrapings/clippings, hair samples, clothing

centerfire rifle head wounds

-temporary cavity within a rigid structure -pressure relieved only by bursting

examples of primary blast injuries

-amputations -body fragmentation -incineration -contusions, lacerations, hemorrhage -pneumothorax, hemothorax -air emboli

what are the characteristics of cartridge cases?

-brass, steel, or aluminum -straight, bottleneck, tapered (obsolete) -rimmed, semi-rimmed, rimless, rebated, belted

a recovered projectile provides information regarding:

-caliber -twist direction -number and width of lands and grooves -individual characteristics imparted by the inner surface of the barrel

characteristics of low explosives

-deflagrate (slower rxn: < 3300 fps) -lower temps -longer duration -needs confinement

characteristics of high explosives

-detonate (faster rxn: > 3300 fps) -higher temps -shorter duration

the impact of tissue type: muscle

-high density -elastic -cohesive

the impact of tissue type: liver

-high density -inelastic -noncohesive

the impact of tissue type: lung

-low density -highly elastic

blast factors affecting injury production

-magnitude -distance -confined vs open area

exit wound characteristics

-marked variability in size and shape -edges can be reapproximated -not always larger than entrance -shored exit

typical features of an entrance wound

-punched out hole -marginal zone without epidermis -grayish/black ring of dirt

elements of an explosion

-rapid conversion of solid or liquid into a gas -gas produced under high temp and pressure -pressure propagated as a radially traveling wave up to 800 m/s -blast front disrupts objects in its path -solid objects reflect and magnify the blast front -subsequent negative pressure wave

examples of secondary blast injuries

-skin lacerations and penetrating injuries -contusions -abrasions -lacerations -dust and dirt tattooing

what two factors establish a bullet's potential

-striking velocity -bullet mass

as the combustion gases have a high content of carbon monoxide, the surrounding tissue often assumes what color?

a bright cherry-red color

firearms injuries are regarded as a special form of ____________ trauma

blunt trauma

permanent cavity ("bullet hole")

bullet crushes and shreds tissue in its path

_________ wounds are rare, even at close range

exit wounds

tertiary blast injuries

flying victim strikes object -other: crush injuries, post-explosion fire

cavity exists 5 to 10 msec with a series of gradually smaller pulsations and contractions before formation of what?

formation of a permanent wound track

"ring of dirt"

indicative of the site where the bullet entered

primary blast injuries

injuries stemming from blast front

small arms: amount of __________________ lost in the tissue is (insufficient/sufficient) to cause remote injury typical of high velocity muzzle weapons

insufficient kinetic energy

a bullet's journey through the skull

internal or external beveling

nonlinear bullet paths are often caused by what?

internal ricochet

high-velocity rifle bullets have a (small/large) temporary cavity

large temporary cavity -11 to 12.5 times the diameter of the projectile

when a projectile penetrates the tissue, it is displaced _______________

laterally/radially -aka: at right angles to the bullet path

what distance is considered close range?

less than 5 feet

in most cases, the wound track in the body is ___________

linear

primary blast injury of the lung

lungs compressed by surrounding rigid structures -delicate alveolar walls rupture

"stopping power"

the potential biological effect of a projectile, in particular, its capacity to prevent a person from moving or attacking

velocity and mass set the limit on what?

the tissue disruption produced

the extent of the temporary cavity and bullet fragmentation determines what?

the ultimate extent of the wound

embolization

transport of bullets or shot pellets within the vascular system

secondary blast injuries

victim struck by flying objects -objects can travel great distances

bullet embolism

weak bullets or pellets may enter a blood vessel on one side without being able to perforate the opposite side so that they remain inside the vessel where they are transported along arteries of veins until they lodge in a more distal part of the systemic or pulmonary circulation