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 fingerprint 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

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