Defining the problem

Forensic sciences play a critical role in the criminal justice system. However, false testimony, exaggerated statistics, and laboratory fraud have all led to wrongful convictions.

Jurors often give forensic evidence significant weight, as the evidence is presented by experts within their fields. In 2009, the National Academy of Forensic Science released a groundbreaking report, “Strengthening Forensic Science in the United States: A Path Forward,” which concluded that DNA analysis is the only forensic technique to “ha[ve] 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.” The report also provided policy recommendations for utilizing forensic techniques in criminal investigations and was critical of several commonly used forensic techniques. 

Examples of problematic forensic disciplines

Hair Microscopy 

What it claims to do: Hair microscopy involves examining hair samples under a microscope to analyze their characteristics . Examiners may identify a suspect by examining hair found at a crime scene under a microscope and comparing it with a suspect’s hair sample.

The Problem: Studies have shown that analysts frequently overstate the certainty of their “matches,” and DNA testing has revealed numerous wrongful convictions based on hair comparison evidence.

Bloodstain Pattern Analysis 

What it claims to do: Bloodstain pattern analysis is used to interpret bloodstains at crime scenes to reconstruct events. Examiners may determine what happened during a violent crime by analyzing the size, shape, and distribution patterns of blood droplets, stains, and spatters.

The Problem: This technique relies heavily on the analyst’s interpretation and experience, rather than validated scientific principles. Analysts often reach different conclusions when examining the same bloodstain patterns, and many factors that affect blood behavior (like surface texture or environmental conditions) are difficult to account for accurately.

Shaken Baby Syndrome

What it claims to do: Shaken Baby Syndrome (SBS), also known as Abusive Head Trauma (AHT), is a medical diagnosis of child abuse. Physicians often diagnose SBS/AHT by observing a “triad” of medical findings (brain swelling, brain bleeding, and retinal hemorrhages) .  Presence of these findings, according to the diagnosing physician, is often caused by violent shaking by a caregiver.

The Problem: Research has shown that the same pattern of injuries once attributed exclusively to shaking can result from various causes, including falls, infections, birth trauma, or pre-existing medical conditions. Biomechanical studies have called into question the validity of the shaking hypothesis.

Other problematic forensic disciplines include forensic odontology (bitemark analysis), arson science, 911 call analysis, shoe print analysis, among others.

How does forensic science go wrong?

Identification, collection, testing, storage, handling, and reporting of evidence can be deliberately or accidentally mishandled at any stage:

At the Crime Scene:

  • Evidence can be planted, destroyed, or mishandled 
  • Proper collection protocols may not be followed 

In the Laboratory: 

  • Evidence can be contaminated
  • Testing may be inadequate or improperly conducted
  • Samples might be consumed entirely
  • Lack of independence of laboratories from law enforcement entities, calling into question the reliability of findings and potential presence of bias.

In Reports and Witness Testimony:

  • Results may be misrepresented
  • Experts may overstate the certainty of their findings
  • Statistical probabilities can be mischaracterized

How to address and remedy faulty forensic science in the criminal justice system

Several reforms could reduce wrongful convictions related to forensic evidence: 

  • Evidence preservation standards: States should require proper preservation and handling of evidence to allow for future testing.
  • Independent oversight: When misconduct is discovered, independent audits should review the analyst’s or laboratory’s other cases for similar errors.
  • Improved scientific standards: Development and enforcement of clear standards within each forensic science discipline.
  • Stronger governance structures: Better oversight to enforce standards and minimize errors.

Case Example: Robert Kaiser

In 2014, Robert Kaiser was wrongfully convicted of murder in the death of his infant son, William. The State’s case relied on the medically-fraught diagnosis of Shaken Baby Syndrome. Following post-conviction proceedings in 2021, a judge found that Robert’s conviction was tainted by false evidence (related to the SBS theory) as well as ineffective assistance of counsel, and vacated his conviction. He was retried in 2025, and ultimately acquitted of all charges, after numerous medical and scientific experts testified on his behalf.