First, the DNA of a test sample must be isolated from that sample, and finally, the DNA must be collected from an individual suspected in the case at hand. DNA is extracted from the crime scene or person and then the size of the DNA sample is determined. As already mentioned, DNA is made up of A, T, G and C. At some point the letters tend to repeat themselves. This set of letters is known as variable number tandem repeats (VNTR). Similar to VNTRs are short tandem repeats (STRs). VNTR sequences (10-100 base pairs) are much longer than STR sequences (2-9 base pairs). STRs are more useful because they can be amplified by PCR, which gives scientists more space to work with when they have a small sample of DNA available. Any biological DNA stored dry or frozen can also be used as a sample. Second, the DNA must be processed so that test results can be generated. After detecting STRs, the number of repeats in the DNA sequence is determined, which is known as genotyping the sample. Finally, the results are compared to determine whether the sample matches that of the