How Are Forensics Used to Solve a Crime?

Updated April 17, 2017

Not long ago, when crimes were committed, there was a good possibility the perpetrator would never be caught. Even if he was caught, without a witness or other damning evidence, the accused likely would never be brought to justice. Many cases went unsolved. At times, innocent people went to prison for crimes they never committed merely because of circumstantial evidence. The last decade has brought substantial changes in forensics. The addition of these new techniques to law enforcement almost make a law-abiding citizen wonder why someone would even attempt to commit a crime.


It has been known for many years that human beings, have a genetic make-up that is theirs and theirs alone. Not another person on the planet has the same deoxyribonucleic acid (DNA) strand. Many cases are solved with DNA. Usually during the commission of a crime, such as rape or murder, the victim defends themselves. Often, these actions leave traces of the assailant's DNA under fingernails or other parts of the victim. Occasionally, semen is left during a rape or the assailant bites the victim. But to what does the DNA get matched? There is a Federal Bureau of Investigation (FBI) registry for DNA called the Combined DNA Index System (CODIS) which is searched for matching DNA evidence. The registry is a valuable resource when trying to pinpoint a person who has committed a crime.

Trace Evidence

Trace evidence is the art of being able to track down residual evidence from a crime scene that, up until recently, had been only frustrating secondary clues detectives could not figure out. Fibres from a carpet found on a body, or some sort of chemical or sap that is on the body but shouldn't be there. With the help of new breakthrough's in trace evidence including a machine called a gas chromatograph mass spectrometer, finding out what the trace is and its source is easier than ever before.

Post Mortem Examination

The best tool in the arsenal to catch criminals is the forensic pathologist and the post mortem examination. The pathologist's job is to find out exactly what killed a victim. While some might find this distasteful, it is an absolute necessity to help catch and punish a killer. Not only does the body tell a story, it can tell how the victim died, how many people were involved and help determine a murder weapon. In cases of accidents, a post mortem can tell if a driver or any other person involved in an accident had any other factors that may have caused the accident, such as a heart attack, stroke or other natural causes that may have caused the accident. In some cases, the pathologist can determine the weapon used by tool marks in the bones of the body.

Forensic Computer Analysis

Some criminals don't realise that by clicking the Delete button, you are not erasing searches or correspondence that could be damning. A law enforcement team is specifically trained to go over a hard drive with a fine-tooth comb to catch someone seeking to destroy electronic evidence of a crime. This assisted in the conviction of one criminal, Scott Petersen, accused of murdering his wife and unborn child. Always the only suspect in his wife's disappearance, his computer was confiscated and what was discovered there, even after he deleted every item, was evidence that linked him to the crime in more ways than one. It takes a long time for the hard drive to rewrite over the disk space and this was used to help convict him of murder.

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About the Author

Annmarie Keller has been a writer for more than 20 years. She has published her work in "Redbook," "Parenting," "Sunset" and "Good Housekeeping." Keller earned a bachelor's degree in English from California State University, Hayward.