Although DNA evidence can seem very convincing, forensic examiners make mistakes. They can run the test incorrectly. They can miss cross-contamination by other DNA. They can misstate the scientific certainty of their findings.
One of the biggest problems facing criminal defendants may be the use of bad expert testimony. Courts are supposed to be gatekeepers for scientific claims. They're supposed to exclude any technical or scientific evidence that isn't "the product of reliable principles and methods" or that isn't supported by the majority of scientists in the given field.
Joe Bryan has not been exonerated, but there is good reason to believe he was wrongfully convicted of the 1985 murder of his wife, Mickey. Bryan was convicted twice despite having been at a conference 120 miles away at the time of the murder. He has served 33 years in prison.
Plea bargaining is a bedrock of our criminal justice system. Governments simply don't have the money to take every criminal defendant to trial. They rely on the fact that a large proportion of defendants will opt for a plea deal if it means less prison time.
Scientifically, it's a pipe dream. It would be convenient if we could train law enforcement officers on how to tell if people are lying, but so far there is no way to do so. That doesn't stop people from trying, though.
Recently, a New Mexico newspaper and the Associated Press covered what sounded like a light-hearted story. Apparently, someone attempted an armed robbery a Pizza Hut store in Las Cruces.
It may be true that no two sets of fingerprints are alike, although there is no actual study showing that. Even if it is true, however, the process of matching fingerprints found at crime scenes to prints from other sources is messy. Most often, crime scene prints are partial or smudged, and there are plenty of prints that are thought common enough to match these.
Each year in the United States, about a million people are pulled over on suspicion of drunk driving. In virtually all of those cases, the driver is asked to blow into a breathalyzer-style machine that estimates their blood-alcohol content. If it's above a certain level, typically 0.08%, the driver is arrested and brought to the precinct for additional testing.
In 2009, the National Academy of Sciences (NAS) issued a blockbuster report challenging the scientific underpinnings of many fields of forensic evidence. The report found that such evidence is rarely supported by rigorous study. Moreover, the analyses are often performed unscientifically, and analysts often overstate the scientific rigor of their evidence during testimony.
In 2009, the National Academy of Sciences issued a blockbuster report on the state of the science in forensic investigation. That report concluded that, "with the exception of nuclear DNA analysis ... no forensic method has been rigorously shown to have the capacity to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source."