Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: gruesome question



At 09:51 AM 5/24/01 -0400, kyle forinash wrote:

The county prosecutor's office called me with the following question.
A car is sitting on an asphalt roadway. Blood is found around and
UNDER a tire. But they don't think the car drove over the blood (no
tracks). Is normal asphalt porous enough for blood to seep under the
tire without moving the tire?

You should be EXTREMELY careful with questions like this. It looks to me
like an ill-conceived question, and an ill-considered answer could cause a
great deal of harm.

I would not touch this with a 10-meter pole without getting a WHOLE LOT
more information.

*) Why does "no tracks" lead them to "think" the care didn't drive over
the blood? Cars move on asphalt all the time without leaving conspicuous
tracks.

*) Was there blood in front of the tire? Maybe the car backed up.

*) Asking about "normal asphalt" won't do. There are many qualitatively
different pavement surfaces that could be called "asphalt".

-- Some asphalt consists of rather widely-separated pebbles held
together by small amounts of tar, leaving all sorts of channels between the
pebbles.
-- In contrast, if the surface has been "re-sealed" a couple of times,
all the channels could be filled in.

Therefore, you REALLY need to see the exact asphalt in question.

*) Similar remarks apply to tires. A new set of knobby tires provides
huge channels through which blood could flow. Bald tires are another story.

*) You also need to see the exact blood pattern in question.
-- If the blood is confined to the channels between pebbles and
between knobs, that's one thing.
-- If it is in places where the rubber of the tire would have been in
conformal contact with the pavement, that's another thing.

*) Are we talking about rivulets of flowing blood and/or splatters?

*) How much blood was near the tire? How much was under the tire?

*) How and when did they determine that there was blood under the
tire? Presumably they had to move the tire to decide that! How did they
move it? What did the scene look like before they moved it?

*) How fresh was the blood when investigators arrived? How fresh would
the blood have been at the time the car did or didn't drive over it? This
matters, because half-congealed blood has hugely different properties than
fresh blood.

*) What was the temperature? What was the humidity? Had it rained recently?

==========================

If you can't do a good job of analyzing the situation, you should answer
"maybe it flowed maybe it didn't" and run away as fast as possible. This
is not some classroom quiz where getting the wrong answer has only trivial
symbolic consequences.