DNA Profiling

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Science has given crime labs new and powerful methods for identifying criminals. DNA profiling is one of the biggest breakthroughs ever made in forensic science.

Everyone's DNA is different. Each cell in a person’s body has a complete complement of their DNA. DNA profiling involves analyzing the DNA from any body cells a criminal leaves behind. One drop of saliva or a single hair is sufficient to profile a suspect’s identity to an accuracy of one in ten million.

When police send a DNA sample to the lab, a special enzyme is used to break strands of DNA into fragments. Then these are separated according to size. Each individual’s DNA breaks into pieces of different lengths and composition. Next, a gene probe tagged with radioactivity is washed over the fragments, and binds to specific places on them. A photograph identifies a pattern of dark bands where the gene probe has stuck to the fragments. The suspect’s DNA fragments are then compared with samples found at the crime scene.

DNA profiling has led to some spectacular convictions. As well, a significant number of convicted rapists has been exonerated using this procedure.

So next time you read about a conviction of a dangerous criminal, be thankful for the work of scientists whose research led to this powerful identification technique.