Do Polygraphs in Maryland Sex Crimes Defense Help or Hurt?

 Posted on September 05, 2025 in Sex Crimes

If you are facing false sex crime allegations in Maryland, you may understandably be desperate to prove your innocence. So, when a law enforcement officer suggests a polygraph test (also known as a "lie detector" test), you may jump at the chance. After all, you are innocent, so why not? Polygraphs are commonly shown in movies and television shows as a tool that definitively separates the truth from lies.

In real courtrooms, however, the story is far more complex. Could a polygraph test help your defense, or could it make things worse? You must understand the limitations of polygraph tests and consult with an experienced Northern Baltimore County, MD criminal defense lawyer who can explain the pros and cons.

How Do Polygraph Tests Work?

Polygraph tests measure involuntary physiological responses, including respiration, pulse rate, blood pressure, and skin conductivity, to determine whether an individual is being truthful or deceptive. Sensors are attached to the body to record changes that are believed to be more intense when the individual is being dishonest.  The process begins with an interview, during which the examiner explains the test, reviews the questions to be asked, and provides the individual with instructions.

Sensors are placed on the individual, and baseline or control questions are asked to determine the individual’s normal physiological responses. Polygraphs are controversial – and not allowed in many jurisdictions – because they measure anxiety rather than actual lies. This can lead to innocent people failing the test out of stress or fear. Conversely, guilty individuals may "pass" the test simply because they are better able to control their responses.  

Do Maryland Courts Allow Polygraph Results?

Most Maryland courts do not allow polygraph results as evidence in criminal trials. The reason for this is a lack of scientific reliability, which could mislead juries into believing that the results of a polygraph are as reliable as those of DNA (Maryland v. King, 2013) or fingerprint tests. Under limited exceptions, polygraphs are sometimes considered in pre-trial negotiations.

How Polygraph Results May Be Used in Maryland Sex Crime Cases

If an individual passes a polygraph test, the defense attorney may use the results as leverage before the trial to convince the prosecutor to consider a plea deal. If the police or prosecutor asks a suspect to take a polygraph test, it is usually a strategy to elicit a confession, and the suspect should refuse. Under some circumstances, the court may require a polygraph as a part of the sex offender treatment or monitoring process. The defense may also use a polygraph to assess whether the client’s testimony is consistent.

The Many Risks Associated with Polygraph Testing

There are too many downsides to polygraph testing for most defense attorneys to allow the prosecution to polygraph their client. False positives, false negatives, nervousness, anxiety, stress, certain medical conditions, some prescription drugs, and poor testing practices can all skew the results of a polygraph.

A suspect may agree to a polygraph, believing it will prove his or her innocence, only to find that it opens the door to more aggressive interrogation tactics. A "failed" test can potentially harm plea negotiations or lead prosecutors to dig in their heels, despite the absence of corroborating evidence. Polygraphs should only be administered under the guidance of a criminal defense attorney, and refusing a test may be better than risking misleading results.

With no polygraph test results, the prosecution is forced to build its case based on evidence and witness credibility, rather than a test that may or may not be accurate. For the most part, polygraph tests are an interrogation tool rather than a truth-seeking device. Police and prosecutors offer the test as a way of pressuring a suspect into making statements he or she would likely not otherwise make.

Contact a Harford County, MD Sex Crimes Lawyer

If you are facing sex crimes charges, never assume that a polygraph will end the case and allow you to go home.  A highly skilled Northern Baltimore County, MD criminal defense attorney from Baltimore Legal Services will comprehensively evaluate the evidence against you and build a case on proven legal strategies. Our attorneys have helped more than 10,000 clients, are available 24/7, and offer a custom flat fee. To schedule your free consultation, call 858-523-8423.