# Forensic Science question?

Okay, our science teacher gave us this challenge to work out the height of a murderer, and the only things she told us were:

- A singe drop of blood was found at the scene

- Criminal had a nosebleed as he was running away from the crime

- The criminals nostril to it's forehead was 15cm

- The only bit of evidence at the crime - the drop of blood - was 11mm in diameter

- The blood droplet fell on a hard, smooth surface (;D)

How could you plan an investigation from that? (Keeping in mind I can only use equipment that can be found in a typical science classroom :P)

Plllllleaseeeeeee Helppppppp, I'll be your BEST friend. ^^

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• K-Dawg
Lv 6

This is a tricky question to get an accurate answer. The question assumes that the offender is standing at full height when the drop of blood fell. If it fell as the offender was running from the scene then chances are they were not standing at full height. If there was a struggle then again, chances are they were not at full height. At best you can calculate a height range for the offender.

The first answer has given you some good starting points, except when they said that it doesn't matter about the surface the drop fell onto. A drop of blood falling onto a hard smooth surface will spatter differently than a drop falling onto a soft surface (such as carpet).

As per "Techniques of Crime Scene Investigation" 5th Edition, the diameter of a blood spot is of little or no value in estimating the distance it has fallen after the first 5 or 6 feet. Beyond this distance the change is to slight to be reliable. Meaning, that if the offender is over 5 foot tall then the diameter is of little relevance.

Of more importance, and providing more information, is the "scalloping" at the edge of the drop of blood. Eg, smooth, small scalloped or large scalloped edges.

Also from the above text: Drops of blood on a plain surface falling from a height of up to 20 inches will have a smooth edge. Drops from a height of 20 to 40 inches will have large and sparse scalloped edges. Drops from a height of 40 to 60 inches will have scalloped edges that are fine and close. Drops from a height of 60 to 80 inches, the scallops are find and close and spatter outward.

The easiest thing to do would be to collect a sample of the blood and send it for DNA analysis. This will provide the identity of the offender. Once you have the identity of the offender you will know their height!

Good luck, I hope this helps you a little.

Source(s): Forensic Scientist

hi i am trying to get best answer :)

right what you do is times (11mm/2 =) 5.5 x by pi

then times the answer by 11mm because of the diameter.

the hard smooth surface is just there to trick you. (not needed excess information.)

now once you got the answer add 15cm because the formula above calculates the hight up to his nostrills so +15 to get to Forehead.

remember that your answer can be close or estimated you should still get the full mark but this is the official way to do it.