General question:
Visually, what differentiates premortem bruising from postmortem pooling? TIA
I have just read a few paper on this, more than I wanted to know but this was one that I found on page 353
HYPOSTASIS AND CONGESTION
Postmortem lividity or hypostasis, which results from pooling of blood after death as a
result of gravity, gives a red/purple appearance
to the areas where the blood is pooled. Usually
there is no diffculty diferentiating hypostasis
from bruising, except where the hypostasis has
a patchy appearance, or bruising is on the back
(cadavers stored in a mortuary in a supine
position are usually found with a substantial
proportion of lividity on the back). The
situation can be compounded by congestive
changes to the body, particularly where congestion is seen in association with deaths involving
some kind of trauma.
Cases involving a mechanical asphyxial
mode of death, such as manual strangulation or
postural (positional) asphyxia, might show
areas of congestion and genuine bruises, the
sizes of which are larger than would be
expected because of the increased volume of
blood in surrounding vessels, which will escape
and contribute to the bruised area. In addition,
congested areas may show postmortem ecchymoses that resemble petechial haemorrhages.
These are often seen within areas of hypostasis.
Although it is recommended that a careful
dissection of the involved area should be
carried out to assess whether, as in the case of
a bruise, the blood has escaped from blood
vessels into the surrounding tissue, occasionally (particularly with pronounced congestion)
this can still be problematical. It is sometimes
useful to move the cadaver into another
position to allow drainage of pooled blood to a
secondary position; true bruising will remain in
the same position
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1731416/pdf/v054p00348.pdf