FORENSIC IMPLICATIONS OF CIRCULATORY SYSTEM
Blood at scene – used to ID victim or perpetrator
Blood type can exclude Nuclear DNA – individual evidence – can
ID (RBCs – no nucleus or DNA; WBCs – have it)
Presumptive Tests
Hemastix – if red stain is blood- plastic strip treated w/ reagent,
moistened w/ dH2O- if turns green – blood
Luminol – mixed w/ H2O2 – is oxidized- to test large area for blood- emits light
Presumptive Tests
Leucomalachite green – similar rxn- in presence of iron, turns blue-green
Kastle-Meyer test – - phenolphthalen turns pink
Scene
Photograph & document scene Collect samples of blood separately from
others If on object, collect whole object If on large object, collect only blood
Scene
To collect dried blood – - use wet swab- use fingertip tape to lift stain- scrape blood into paper bag
If wet blood, need to dry first
Collect evidence from suspect Samples = control or known sample for
comparison Used to make a DNA profile to ID
Lividity
= pooling of blood in the direction of gravity
Livor mortis = postmortem change in color caused by lividity
Appears 30 min – 2 hours after death Not fixed yet – pooled blood can shift if
pressed Fixed after 12 hours – irreversible and
permanent
Lividity
B/c fixed – can be used to determine if body was moved after death
Patches of lividity in different areas of body indicate body was moved
After fixed, check position of body with lividity pattern
Lividity
Bluish-purple to reddish-purple near ground
Becomes darker over time b/c oxygen separates from hemoglobin -
> purple pigment (deoxyhemoglobin) Areas away from ground - pink
Clues from Lividity
Bright red - CO poisoning Bright pink – hypothermia, body
refrigerated shortly after death, cyanide poisoning
Dark brown – lethal doses of nitrates, aniline, & potassium chlorate (forms meth-hemoglobin)
If arm or leg hanging when person dies, petechiae (= small red dots underneath surface of skin) may show
Blood Spatter
Position of victim & perpetrator Use laws of physics Blood – high viscosity (= liquid’s
resistance to flow) Blood – high surface tension – allows
blood to retain its shape when contacts other object
Blood Spatter
Velocity blood travels as it leaves body combines with gravity producing a certain path
Low-velocity spatter- if person moves after losing blood
from stab wound, blood falls down large droplets
Blood Spatter
Medium-velocity spatter- from blunt force trauma - blood spurts out from body
Blood Spatter
High - velocity spatter- from gunshot wounds- tiny droplets, like a fine spray
Blood Spatter
Arterial spray - based on heartbeat pattern
Blood Spatter
Useful in determining: - position of victim - type of weapon or tool used - # of times victim was hit, shot, or stabbed - if victim moved after assault
Blood Spatter
After evaluation, may determine: Events of crime Sequence of events Who was or was not present