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Why is forensic evidence often wrong?

On Behalf of | Jul 19, 2017 | Blog |

Television crime shows have given Americans the impression that DNA evidence is nearly infallible. Recent studies indicate that not only is forensic evidence not perfect, it’s actually very prone to error.

Two major reports have examined what is wrong with forensic evidence. The first study was conducted in 2009 by the National Academy of Sciences. The second study was published in 2016 by the President’s Council of Advisors on Science and Technology.

The 2016 report says, “Forensic science has been used primarily in two phases of the criminal-justice process: investigation, which seeks to identify the likely perpetrator of a crime, and prosecution, which seeks to prove the guilt of a defendant beyond a reasonable doubt.” The report examined the research that provides the foundation for forensics and made recommendations to federal law enforcement agencies on how to improve the use of forensics. 

The report’s conclusion — that forensic analysis often is flawed — has profound implications for the U.S. judicial system.

5 common forensics mistakes

Here are five ways mistakes are made with forensics, according to the nonprofit legal organization The Innocence Project.

1. Unreliable methods are used in crime labs. Some processes (the analysis of bite marks, for example) do not produce consistently accurate results.

2. Simple mistakes are made, like mixing up or contaminating samples. It’s sometime forgotten that forensic investigation is done by humans. When humans are involved in anything, mistakes are made. 

3. Misconduct. It is truly tragic, but in some cases, forensic analysts have lied about results.

4. Inadequate research into the accuracy of DNA processes and analysis.

5. Misleading testimony. This happens in three ways:

  • People giving testimony in court exaggerate the similarities between evidence at a crime scene and evidence from an individual.
  • Testimony omits evidence that would exclude a person as a suspect.
  • People giving testimony don’t explain the limitations of forensics.

What does this mean for the accused?

The bottom line is this: forensic evidence is often wrong. For people accused of crimes, an effective criminal defense attorney is still the best hope for evaluating and finding flaws in evidence.


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