"Leo is a professor of law and psychology at the University of San Francisco." He has testified as an expert on the subjects of police interrogation, psychological coercion, and false confessions well over three hundred times. His testimony was admitted as expert testimony on those subjects in this case. On cross-examination, Leo agreed that in a few cases his testimony was not permitted by the court. In 2008 a Michigan court found his methodology unreliable.

Leo distinguished interviews, which involve open-ended questions, from interrogations, which are typically accusatory. Interrogations are "guilt presumptive" because they are "typically preceded by an investigation in which the police or agents conclude that a person committed the crime." ".. Police then interrogate that person with the goal of obtaining a confession". A typical method of doing so involves isolating the suspect, building rapport with the suspect, and then accusing and confronting the suspect.

Leo testified that an interrogation becomes psychologically coercive when the suspect perceives that he has "no meaningful choice but to do what they are being pressured and persuaded or demanded to do." .. Interrogators employ various psychological techniques.

They include:

Falsely informing a suspect that the interrogators have evidence linking them to the crime, to encourage admissions. Leo testified that false evidence ploys are often a "real problem in false confession cases." ..

Providing inducements to persuade a suspect that it is in their best interest to stop denying. Inducements can also appeal to morality or conscience.

Minimizing the suspect's involvement to make the suspect think that if they confess, the consequences will be minimal..

Maximizing the potential consequences as a threat for continuing to deny involvement and not cooperating..

A suspect's cognitive and intellectual deficits and personality traits can make them more vulnerable to psychological coercion..

Leo testified that interrogations can also be problematic when the interrogator discloses non-public details about the crime, which are later repeated back by the suspect demonstrating guilt..

Leo also testified that the videotaped confession shows Hayat was fatigued and sleep-deprived.. Leo testified that Hayat's requests to see his father and go home, which were effectively denied, demonstrate a problem in false confessions that the suspect understands that the only way to put an end to the interrogation or to go home is to say what the interrogator is looking for...

Leo next considered frequent statements made to Hayat that if he cooperated, interrogators should be able to help him and things are going to be a lot better for you. . An interrogator also told Hayat, If I'm gonna make an argument for you, who I, I think is not an important part in this.... I need you to tell me details about targets.... And, this is where I need your memory to come back.. Leo testified that these statements show an attempt by interrogators to suggest that there is a quid pro quo in exchange for confession.

Asking Hayat whether he may have gone to a jihadist training camp thinking that he was actually going to a religious education camp is an example of the minimization risk factor.. Interrogators attempted to have Hayat admit he attended a camp by suggesting that Hayat's intentions in going to a camp might be considered.

In summary, Leo testified that the following risk factors for false confessions were present in the recorded portion of Hayat's interrogation: a false evidence ploy, inducements with the suggestion of benefits for cooperation, sleep deprivation, and the lengthy interrogation.