A police fingerprint sheet used to house a criminal's print
Before & After:
Crime Solving
Before: Without the class of forensic science, in the police force, police had only their wit, and their gun holstered closely to their side. They could only hope witnesses were telling the truth about the crime, and testified similarly. This was clearly not always effective, as any number of people could lie about one case. If more than one "witness" agreed with a criminal stating they were innocent, then there would be a good chance of the offender never being charged.
After: DNA has let the world of police investigation advance greatly over the few years after its discovery. Not only does DNA help find criminals by scanning fingerprints or blood, but it also helps exonerate people who were wrongly convicted of the crimes committed. If the police force collect a sample of a possible offender at their crime scene, they either need to call in the person they think is a suspect and take their blood or fingerprint, or the criminal must already be in the Combined DNA Index System, otherwise abbreviated as CODIS. This is an FBI program allowing all states access to the criminal justice DNA databases, as well as the software used for running the databases.
There are still many cases that have been left unsolved. Even with forensic science, criminals such as the Zodiac Killer and D.B. Cooper have yet to be found. DNA has, however, still caught major criminals. The Golden State Killer was caught more than 32 years after their string of murders and rapes through a 10 year period. This was through GEDmatch, an online service made to compare DNA samples from multiple different testing companies. Websites such as 23andMe and Ancestry.com have sometimes been helping unknowingly. Even if a distant relative of a crimimal enters their DNA into any one of the numerous testing sites, then the police would be able to aquire a warrant in order to look at a person's DNA. This would help them trace the DNA down the family tree until the possible suspect is deemed guilty or not.
Logo for the FBI DNA Database, Wikipedia