The 1900s saw the evolution of perhaps one of the most important things to man - DNA.

DNA (deoxyribonucleic acid) was first discovered in the mid-to-late 1800s by Swiss researcher Friedrich Miescher - not by James Watson and Francis Crick. This is a common misconception but James Watson and Francis Crick only furthered the world's knowledge of DNA. They discovered the structure of DNA in 1953.

Friedrich Miescher found the "molecule of life" by mistake. He was actually looking to gain information on white blood cells. During his experimentation, he found DNA yet he did not share it with the scientific community for some years. Even after he shared his findings, it was relatively ignored for some time.

Of course, as we have heard of it in the twenty-first century, scientists eventually came around though knowledge of it was still limited. If the information scientists had was limited, the information the rest of the world had was even more so. 

In fact, it wasn't until 1984 that Sir Alec Jeffreys, a British geneticist at the University of Leicester, tested DNA and determined that it was essentially a genetic fingerprint. It was at this time that other entities (i.e. law enforcement and courts) could finally use this to their advantage. They didn't wait long as the first use of DNA was in 1985 in England during an immigration case. A British boy whose family was originally from Ghana had difficulty returning to England. The son left home and was stopped from going back to the United Kingdom due to a "forged" passport. DNA confirmed he was who he said.

The next year, DNA was used by law enforcement following the rape and murder of two teens. A suspect was in custody and confessed to only one of the murders even though it was clear one person committed both. Sir Alec Jeffreys was asked to do some profiling on the suspect and the semen found on the victims. The semen on both girls was found to be from one man and that man was not the individual who confessed. Still, law enforcement was able to find their killer with DNA.

The United States was able to use DNA testing in 1987 when they convicted a man in Florida for rape. A few years later, in 1989, the United States had its first case overturned based on DNA evidence.

The 1990s saw the creation of DNA databases. In 1995, the U.K. created its database and the FBI created the U.S. national DNA database in 1998. As you can suspect, the use of DNA skyrocketed, so much so that law enforcement can no longer keep up. In 2000, the Federal DNA Database Unit was established as a result of the DNA Backlog Elimination Act.

Twenty years later, we still have this problem but DNA has come a long way. Some businesses are now focusing on attempting to make familial matches though this still is not regularly used by law enforcement at this time.

That said, what does this have to do with you? Maybe nothing. However, if you are writing about crime and using DNA, make sure to keep in mind the timeline and development of the use of DNA by law enforcement. My goal is to give writers a reference to make sure their work is historically accurate.