Question

A burglar in a huff forgot to wipe off his blood stains from the place of crime where he was involved in a theft. Name the technique which can help in identifying the burglar from the blood stains. Describe the technique.

Answer 1

Hint: Blood is one of the most important biological evidence found at the crime scene. It contains vital information thus its analysis can lead to identifying the culprit. It can also help to understand the circumstances under which the crime has been committed.

Complete answer:
If a red stain is found at the crime scene, the first step of the Investigating Officer is to determine whether it is blood or not. After confirming the presence of blood, DNA profiling should be done to check its source. If the burglar forgot to wipe off his bloodstains from the crime scene, his bloodstains could be used by the Investigating Officer to identify him by using DNA profiling.
DNA profiling, commonly known as DNA fingerprinting, is a technique to identify an individual through his DNA as no two individuals (except the identical twins) can have exactly the same nucleotide sequence present in DNA. There is a sequence of nucleotides which is repeated over and over again, and is unique in each individual. These regions of repeated sequence are known as Variable Number of Tandem Repeats (VNTRs).
In DNA fingerprinting, DNA is first extracted out from the source (blood in this case) by using various techniques such as Restriction Fragment Length Polymorphism (RFLP) which is most commonly used. It involves using restriction enzymes to cut DNA surrounding the VNTRs. After extraction and fragmentation of DNA, its fragments are separated according to their sizes using gel electrophoresis and then transferred onto a membrane, and probes are added to that membrane (Southern Blotting). Probes get attached to the complementary DNA fragments and then finally, matched with the sample DNA.

Note:
Blood analysis can also provide essential information that helps in the legal determination of crime. Blood spatter analysis is the analysis of the blood pattern to determine the sequence of events.