Question: how do you use blood to identify someone

Anastasia Aliferi answered on 19 Nov 2019:

We analyze blood and get DNA out of it, which is basically a code that tells our body how to work. This code is a little bit different for each person and in this way, if we have DNA from some blood found at a crime scene and DNA from a suspect, we can see if the two match and identify that suspect as the person who left that blood at the crime scene! This is something the police can already use, but my project at the moment is about doing something a little more tricky. I’m actually trying to see what we can do in cases when we don’t have a suspect to match the DNA to! I’m basically trying to get as much information as I can out of that drop of blood that can help the police narrow down their search. I’m trying to figure out the age of the person who left that blood drop, how they look like (for example the colour of their eyes) and where they come from.