how is the knowledge of fingerprints, DNA...

[MeGz]

...and blood used to solve crimes?

[Principessa]

Fingerprints and DNA (found in blood) identifies the person who committed the crime. Fingerprints and DNA are unique to that individual. Especially if the perpetrator committed a prior crime and had his/her fingerprints documented, it is an easy match to identify who committed the crime. DNA is relatively new and very expensive to analyze, but it's a 100% way to prove the identity of the criminal. No DNA (except for identical twins is the same).

[Ridhima]

when a person touches an object, he leave s his finger prints on it
there is no human in world who don`t have fingerprints
except one and this is known as dermatopothia pigmentosa reticularis(dpr)
blood has some proteins called dna which when checked by some persons body help in detecting criminal

[Penelope]

Well, everyone in the world has a reported fingerprint and blood test. sooo if someone got caught in a burglary their fingerprint would prove that they were there. Or if blood was spilled it would show whose it was.

[Robert and Susan]

there are no two exactly alike....so weeding out suspect is fool proof....

[Edwin]

Finger prints as with DNA, only prove the person where present or not, it will not prove the person committed the crime. for that we are back to detective work and good hard research. How many prints are on a classroom door or what DNA may be found in a hospital bin.

Prints are lass accurate though very good. DNA is you personal Bar-code and its unique to you. whether you committed the crime or where their some time before will have to be proved by your prosecution.