Leading questions—questions worded in such a way as to suggest a particular answer—can yield unreliable testimony either by design, as when a lawyer tries to trick a witness into affirming a particular version of the evidence of a case, or by accident, when a questioner unintentionally prejudices the witness's response. For this reason, a judge can disallow such questions in the courtroom interrogation of witnesses. But their exclusion from the courtroom by no means eliminates the remote effects of earlier leading questions on eyewitness testimony. Alarmingly, the beliefs about an event that a witness brings to the courtroom may often be adulterated by the effects of leading questions that were introduced intentionally or unintentionally by lawyers, police investigators, reporters, or others with whom the witness has already interacted.

Recent studies have confirmed the ability of leading questions to alter the details of our memories and have led to a better understanding of how this process occurs and, perhaps, of the conditions that make for greater risks that an eyewitness's memories have been tainted by leading questions. These studies suggest that not all details of our experiences become clearly or stably stored in memory—only those to which we give adequate attention. Moreover, experimental evidence indicates that if subtly introduced new data involving remembered events do not actively conflict with our stored memory data, we tend to process such new data similarly whether they correspond to details as we remember them, or to gaps in those details. In the former case, we often retain the new data as a reinforcement of the corresponding aspect of the memory, and in the latter case, we often retain them as a construction to fill the corresponding gap. An eyewitness who is asked, prior to courtroom testimony, "How fast was the car going when it passed the stop sign?" may respond to the query about speed without addressing the question of the stop sign. But the "stop sign" datum has now been introduced, and when later recalled, perhaps during courtroom testimony, it may be processed as belonging to the original memory even if the witness actually saw no stop sign.

The farther removed from the event, the greater the chance of a vague or incomplete recollection and the greater the likelihood of newly suggested information blending with original memories. Since we can be more easily misled with respect to fainter and more uncertain memories, tangential details are more apt to become constructed out of subsequently introduced information than are more central details. But what is tangential to a witness's original experience of an event may nevertheless be crucial to the courtroom issues that the witness's memories are supposed to resolve. For example, a perpetrator's shirt color or hairstyle might be tangential to one's shocked observance of an armed robbery, but later those factors might be crucial to establishing the identity of the perpetrator.