Law enforcement agencies and legal professionals often have to rely on witness statements. Undetected errors in witnesses' statements, however, could impede the accurate reconstruction of a crime and lead to the incrimination of innocent suspects. Here, we examined whether witnesses can detect manipulations in their written statements. We expect that writing a statement could provide a good means for discrimination between what is truly recalled and what is an error. This is because writing allows to monitor and control the previously produced information. In 3 experiments, participants watched a mock crime film and subsequently provided a written statement of what they had witnessed. Following a delay of several minutes (Experiment 1), 48 hr (Experiment 2), or 1 month (Experiment 3), participants were exposed to and interviewed about their testimony. Unknown to them, they were confronted with statements, which included 4 secretly manipulated details. Participants' missed a substantial number of manipulations in their written statements. Importantly, the detection rates varied as a function of delay (Experiments 1 and 2: 74–89%; Experiment 3: 36%–52%). Detection rates also varied as a function of the type of details that were manipulated. Our findings indicate that writing a statement comes with limited benefits in witnesses' ability to detect errors in their statements.