Case File 265 · Investigation Psychology

How Does Sleep Deprivation Affect Memory and Questioning?

By Murder Book Editorial TeamPublished by Gungrounds, the studio making Murder BookPublished 3 October 2026Updated 3 October 2026

Sleep deprivation weakens memory, impairs judgement and increases susceptibility to suggestion, all of which matter when a person is being questioned. Research shows that people who have not slept are significantly more likely to produce false memories, more vulnerable to misleading information, and more willing to confess to things they did not do. A study found that sleep-deprived participants were 4.5 times more likely to sign a false confession than rested ones. These effects are not about willpower or character. Sleep loss degrades the cognitive processes, attention, working memory and executive function, that a person needs to give an accurate account and to resist pressure. Since many real-world interviews and interrogations happen late at night or after long waits, sleep deprivation is not a rare edge case; it is a routine factor that investigations need to account for.

Key takeaways

Sleep-deprived people are 4.5 times more likely to falsely confess in experimental settings.
Sleep loss increases susceptibility to the misinformation effect and to false memory formation.
Fatigue impairs the executive functions needed to resist leading questions and social pressure.
Studies estimate that around 17% of interrogations occur during typical sleep hours, between midnight and 8 a.m.
Recording interview timing and the suspect's or witness's sleep history is a basic safeguard.

How does sleep deprivation affect memory?

Sleep plays a critical role in memory consolidation, the process by which recently encoded experiences are stabilised into long-term storage. When sleep is disrupted or absent, this consolidation is impaired. But sleep deprivation also degrades memory at the encoding stage: a tired person pays less attention, processes information less deeply and is more prone to errors in source monitoring, the ability to distinguish where a piece of information came from.

Research by Frenda, Patihis, Loftus and colleagues found that sleep deprivation during the encoding of an event significantly increased susceptibility to false memories. Participants who were sleep-deprived when they first viewed photographs of a crime scene were more likely to later report false details that had been introduced through misleading narratives. The effect was specific to encoding: sleep deprivation after the event did not produce the same increase in false memories.

This has direct implications for witnesses and suspects who were already tired when an event occurred or when they were first exposed to information about it.

What about false confessions?

The link between sleep deprivation and false confessions has been tested directly. In a study by Frenda, Berkowitz, Loftus and Fenn, participants completed a computer task with a clear instruction not to press a certain key. They were later accused of having pressed it. Among those who had been sleep-deprived, 50% signed a statement falsely confessing to the prohibited action, compared to 18% of rested participants.

The authors attributed this to the combined effects of fatigue on multiple cognitive systems. Sleep-deprived people have reduced capacity to evaluate the plausibility of accusations, weaker resistance to social pressure, and impaired ability to search their own memory for evidence that the accusation is false. When someone is exhausted and being pressed to agree, the path of least resistance is to comply, a dynamic explored in why do innocent people confess?.

How does fatigue interact with interrogation?

Interrogation is cognitively demanding. A person being questioned must simultaneously recall events, monitor the questions for bias, evaluate the implications of their answers and resist pressure to agree with suggestions they believe are wrong. All of these tasks depend on executive functions that are among the first capacities degraded by sleep loss.

Studies of known false confession cases have found that many occurred after interrogations lasting more than twelve hours, with some exceeding twenty-four hours. Research also estimates that approximately 17% of interrogations occur during typical sleep hours, between midnight and 8 a.m. These timing patterns mean that a significant proportion of people being questioned are doing so while fatigued, even before any deliberate pressure is applied.

The problem is compounded when interrogation techniques involve:

Repetition. Asking the same question repeatedly is more likely to produce acquiescence from a fatigued person.
Maximisation and minimisation. Techniques that exaggerate the evidence or downplay the consequences are more effective against someone whose critical thinking is impaired.
Long sessions. Extended questioning without adequate rest breaks increases fatigue over time, progressively weakening the person's ability to give reliable answers.

Does sleep deprivation affect witnesses too?

Yes. The effects are not limited to suspects. A witness who was sleep-deprived at the time of an event may encode a weaker, less detailed memory. A witness questioned while fatigued may be more susceptible to leading questions and more likely to accept suggested details as genuine memories, a pattern closely related to the misinformation effect.

Sleep-deprived witnesses may also appear less coherent, hesitant or inconsistent, characteristics that can be misread as signs of deception when they are actually symptoms of fatigue. The risk of misinterpreting these cues is one reason that no single behaviour reliably indicates deception.

What safeguards help?

Several practical measures can reduce the risk that sleep deprivation will compromise the quality of evidence:

Record the time of interviews and the person's self-reported sleep history. This provides context for evaluating the account later.
Avoid unnecessary late-night or prolonged questioning. If an interview must be conducted at an unusual hour, the fatigue factor should be acknowledged.
Provide rest breaks during extended sessions, and be aware that compliance may increase as fatigue accumulates.
Use non-coercive, information-gathering approaches rather than accusatorial techniques, since fatigued people are more susceptible to pressure.
Record the interview. A recording allows later review of whether the person's responses showed signs of fatigue-related compliance rather than genuine recall or voluntary confession.

These safeguards do not eliminate the effects of sleep deprivation, but they make those effects visible so they can be weighed properly.

How does Murder Book reflect the pressure of questioning?

Murder Book: The Art of Interrogation is an upcoming narrative interrogation game from Gungrounds, an independent studio in Zagreb, Croatia. Its cases are inspired by real police footage and psychological interviews, and they present players with situations where behaviour during questioning does not have a simple interpretation. A hesitant or compliant response might mean guilt, or it might mean the person is exhausted, confused or simply cooperative.

The game asks players to read behaviour in context rather than relying on surface cues, which mirrors the research on sleep deprivation: what looks like an admission may be fatigue, and what looks like evasion may be a person struggling to think clearly. Cases are designed for focused 5–10-minute sessions. Murder Book is in development for PC (Steam) and mobile, with release currently planned for the end of Q2 2027.