Smoking marijuana makes a person more likely to recall false memories and information, resulting in a higher likelihood of false confessions and inaccurate witness statements when pursuing criminal cases, according to new research.
In a study of 64 healthy occasional cannabis users, an international team of researchers determined that smoking THC, the psychoactive chemical in cannabis, can lead to people recalling fake or implanted memories.
“Testimonies by eyewitnesses or suspects are oftentimes the only piece of evidence that triers of fact can use for legal decision making, and, thus, gathering reliable testimony is crucial. However, memory performance is imperfect, resulting sometimes in false memories,” write the authors, adding that such false memories can have disastrous consequences in legal cases, such as wrongful convictions or false accusations.
To test the impact of cannabis use on recalling memories, study participants were given a dose of the drug and were then asked to participate in three separate memory tests involving reading, reciting words, and recalling events from virtual reality-based scenarios. Researchers phrased their questions in a way to influence the volunteers’ memories, sometimes even introducing fake information. Each test was performed immediately after a participant smoked and again one week later.
Writing in the journal of the Proceedings of the National Academy of Sciences, study authors found evidence that suggests using cannabis consistently increases a person’s susceptibility to form false memories based on false information. In particular, two types of memories were noted: “spontaneous” memories that arise from cognitive processes and “suggestion-based” memories that occur from external suggestions.
“Cannabis seems to increase false-memory proneness,” write the authors. “Our findings have implications for how and when the police should interview suspects and eyewitnesses.”
Cannabis is the most widely used illicit drug in the world. Though previous studies have associated its use with memory impairments and distortion, little evidence has connected cannabis with procuring false confessions and witness statements in criminal investigations. Drug testing is often a common protocol with suspects, but not with witnesses or victims.
“The results have implications for police, legal professionals, and policymakers with regard to the treatment of cannabis-intoxicated witnesses and suspects and the validity of their statements,” note the researchers. “With the growing global acceptance of cannabis and its widespread use by eyewitnesses and suspects in legal cases, understanding the popular drug’s ramifications for memory is a pressing need.”
It is possible that misinformation can lead to false confessions in criminal interrogations when the accused is under the use of cannabis. The researchers add that their findings stress the need to further study cannabis use in facilitating false-memory production.