The very idea of a machine that candetect lies is fascinating and intriguing. But are polygraph results actually admissible as evidence in U.S. courts?
The short answer is no, polygraph results are rarely admissible in court. But the full story is more nuanced. Let’s take a look at the complex legal landscape surrounding polygraphs in the American judicial system.
A Brief History of Polygraphs in U.S. Law
Before examining their current legal status, it helps to understand their origins in the legal sphere.
- The polygraph was invented in 1921 by John Larson, a medical student at the University of California, Berkeley and a police officer.
- In 1923, Larson’s device was used in a criminal case for the first time, during the murder investigation of a retired Berkeley police chief.
- Throughout the 1920s and 30s, polygraphs started gaining limited acceptance in law enforcement.
- In 1946, the U.S. Supreme Court ruled on the first major case involving polygraph admissibility, Frye v. United States. This landmark case established the “general acceptance” test that remains influential today.
- During the Cold War, concern over espionage led U.S. agencies to expand polygraph use for security screening.
- By the 1960s, all federal law enforcement agencies used polygraphs to some degree. Private sector use also increased.
- But by the 1970s, strong skepticism of polygraph accuracy emerged, led by academic researchers.
So by the late 20th century, polygraphs had become common in law enforcement contexts but faced rising scientific criticism. This set the stage for legal battles over their admissibility.
The Legal Landscape Today
Currently, results are generally inadmissible as evidence in federal and state courts. But there are some exceptions.
Federal Courts
The prevailing precedent at the federal level comes from the U.S. Supreme Court’s 1998 decision in United States v. Scheffer. The Court ruled that a blanket exclusion of polygraph evidence did not violate the defendant’s constitutional rights. Citing concerns about polygraph unreliability and the risk of usurping the jury’s role, the Court affirmed the discretion of lower courts to bar polygraph evidence.
However, Scheffer still left the door open for evidence to be admitted under certain circumstances:
- If the prosecution and defense both agree to allow polygraph results
- In probation or supervised release revocation hearings
- When evaluating pre-trial bail or sentencing
So federal courts may make limited exceptions, but generally do not allow evidence at trial.
State Courts
Polygraph admissibility varies more widely at the state level, since states set their own evidentiary standards. Roughly 25 states partially allow polygraph results, while 25 states generally prohibit them.
For example:
- New Mexico allows polygraph evidence if both parties consent
- Massachusetts bars polygraph evidence entirely
- Ohio only permits it in civil lawsuits, not criminal cases
These are the states that may accept evidence in court:
- Alaska
- Colorado
- Georgia
- Idaho
- Indiana
- Kansas
- Kentucky
- Minnesota
- Missouri
- Nebraska
- New Hampshire
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- South Dakota
- Tennessee
- Texas
- Utah
- Virginia
- West Virginia
Some tried crafting compromise rules to restrict polygraph use, rather than outright banning it. For instance, requiring the examiner be licensed and having at least 5 years experience.
But state policies remain complex and inconsistent. Most either fully prohibit polygraphs or only make narrow exceptions.
Why Are Polygraphs Inadmissible? Reliability Concerns
Courts cite several key reasons why they are generally barred as evidence:
1. Controversial Accuracy
- Polygraph testing has no universally accepted accuracy rate. Reported accuracy varies widely.
- There is disagreement between polygraph advocates and detractors on how to interpret accuracy statistics.
- Critics argue the error rate is unacceptably high for a method that can determine guilt or innocence.
- Without scientific consensus on accuracy, reliability is doubtful.
2. Lack of Standardization
- There is no single universally accepted polygraph testing procedure or instrument. Many techniques exist.
- Examiner’s training and testing methods vary greatly. No licensing is required in most jurisdictions.
- With much variability, quality control is difficult.
3. Subjectivity in Interpreting Results
- There is room for variability in how different examiners interpret polygraph data.
- No minimum standards exist for result interpretation, opening the door to subjectivity.
- Varying interpretations undermine consistency.
Due to these major concerns, most U.S. courts remain unconvinced polygraphs are scientifically sound enough for admission as evidence.
Notable Exceptions
While results are generally barred in court, there are some notable exceptions:
- Military trials – In certain military court proceedings, polygraphs are more readily allowed as evidence. However, the rules vary between different branches of the military.
- Probation hearings – Some states allow polygraphs when deciding whether to revoke probation or parole. Failing a polygraph can be treated as a violation of probation terms.
- Pre-employment screening – Private companies are free to use polygraphs when screening job candidates, as long as certain employment laws are followed. Results can influence hiring decisions.
- Security clearance evaluations – When making security clearance determinations, the U.S. government sometimes uses polygraphs to assess risk factors.
So there are limited contexts outside of criminal trials where polygraphs maintain some permissible uses. But standards of evidence are lowered in these settings.
Ongoing Controversies and Developments
Some recent developments include:
- New trial approaches like having opposing expert witnesses debate polygraph reliability before the jury.
- Using polygraph evidence not to demonstrate “truthfulness”, but only as proof that an examination was performed.
- Efforts to improve polygraph accuracy and standardization, like research into using AI-powered sensors.
- Proposals to permit conditional admissibility, allowing polygraphs if certain accuracy and examiner quality standards are met.
While wholesale polygraph evidence is unlikely to be permitted in court anytime soon, incremental changes in both directions continue.
The Complex Realities
Polygraph admissibility in U.S. courts is a complex, nuanced topic. There are no absolute yes or no answers. Here are some key points reflecting the realities:
- A blanket federal ban is unconstitutional, but general prohibition is still the prevailing policy.
- Most states exclude polygraphs, but some allow exceptions or conditional uses. State rules vary widely.
- Reliability concerns dominate, but improvements in polygraph techniques and supervision may incrementally boost admissibility over time.
- Courts are highly skeptical of using polygraphs as direct evidence of truth-telling, but indirect and limited uses occur in specific scenarios.
- Private sector usage and consequences are less regulated compared to criminal courts.
- Ongoing legal debates and developments continue around expanding vs restricting polygraph use.
The underlying tension between the desire for more certain proof vs doubts about reliability seems destined to fuel lively debate for years to come.
