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Be aware: Forensic evidence isn’t always accurate

On Behalf of | Aug 10, 2021 | Criminal Defense |

Sometimes, when people are arrested, police officers tell them they have been caught dead to rights. There is forensic evidence – fingerprints, bloodstains, DNA, hair, fibers or other tests that clearly indicate guilt. The suspect might as well give up and plead guilty.

You should never plead guilty to any crime without talking to an attorney. One good reason is that forensic evidence, which often involves matching a sample from the crime scene to a sample from the defendant, is not always accurate. With a proper defense at trial, a jury could be persuaded that the evidence is not enough to convict you.

Two major investigations find many common types of forensic evidence highly questionable

A decade ago, in an effort to get a sense of how reliable forensic evidence was, the National Academy of Sciences undertook a major review for the Justice Department. That led to a seminal 2009 report by the National Research Council (NRC).

The NRC noted that there are many talented and dedicated people in the field of forensic science, but it found that many of the techniques commonly used in criminal trials are not backed up by sufficient science. Moreover, the NRC found that, in some cases, mistaken or exaggerated testimony about forensic test results had led to the wrongful conviction of innocent people.

There is no mandatory standardization, certification or accreditation of forensic science professionals, the report said, which means that the quality of forensic evidence varies widely by jurisdiction.

Further, the term “forensic science” encompasses a broad range of techniques, some of which are more reliable than others. There is a wide variety of techniques and methodologies used, some of which are non-scientific. Further, the tests can sometimes be interpreted in a pro-prosecution or biased fashion, even though forensic scientists are not supposed to take sides in criminal cases.

The NRC concluded that more research is needed to establish proper limits, measures and performance standards for many common forensic techniques. It also concluded that forensic evidence should only be admissible in court when that evidence can be shown to be backed up by science and not exaggerated by the forensic technician who testifies.

Then, in 2016, the President’s Council of Advisors on Science and Technology followed up with a report of its own. That report concurred with the NRC that more rigorous scientific standards are needed to back up many common types of forensic evidence.

It went further, however. It found that so-called “feature comparison” analyses, where a sample from the crime scene is compared with a source sample from a defendant, are not reliable. They are not backed up by sufficient science. They can be tainted by bias or error by the technician.

Common feature comparison tests include:

  • Latent fingerprint analysis
  • Hair comparison, including microscopic hair analysis
  • Firearms/spent ammunition (“ballistics”)
  • Tool mark matching
  • Bite mark matching
  • Shoeprint matching
  • Tire track analysis
  • Handwriting analysis
  • Some DNA tests

In addition to the tests themselves being scientifically unreliable, the Council found that forensic analysts routinely overstate the scientific certainty of their results when testifying in court cases.

In other words, a lot of forensic science has been found foundationally invalid AND invalid in its application.

Forensic evidence is not as good as it seems on CSI

If you have been accused of a crime based on scientific or forensic evidence, you should not panic. You should contact an experienced criminal defense attorney right away. Your attorney may be able to present a comprehensive defense against the scientific evidence the prosecution claims to have. It could also be useful to have your own forensic expert to counter the expert presented by the prosecution. You owe it to yourself to fight.


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