Eyewitnesses under the influence of weed

Dutch newspaper de Volkskrant published an article today, ‘Does a joint make an eyewitness less reliable?‘, about a study by ALLP member Annelies Vredeveldt, in collaboration with a colleague at Florida International University and two VU students.

Eyewitnesses of crime are often under the influence of drugs or alcohol. For example, an estimated 30 to 50% of people in the Dutch nightlife scene have smoked weed. Yet, little is known about the effects of cannabis on eyewitness memory. This new study shows that people under the influence of weed remember significantly less about a robbery they have witnessed, but do not make more mistakes than sober people.

Eyewitnesses who had smoked weed were no better or worse at identifying a perpetrator from a police line-up, but a surprising finding was that they were better at judging whether their identification was correct. They were more confident in their correct decisions, and less confident in their incorrect decisions.

For police investigators and legal professionals, it is important to know how drugs influence eyewitness statements and identifications, particularly because in certain cases (e.g., assault in the nightlife scene), intoxicated eyewitnesses may be all they have.

For more information, see also the scientific journal article on this study (available open-access).