Episodic Memory – Arizona Forensic Services, LLC

Snap Shot

The question: What is episodic memory, the memory for a particular event at a particular place and time, and what does research on how such memories are formed, bound together, and retrieved mean for testimony about what happened on one occasion?

What the research shows: Episodic memories are built from separate elements (what, where, when, and from what source) that must be bound together and are reconstructed at retrieval, so details can be lost, moved to the wrong occasion, or borrowed from later information. Gist and central features of a distinctive event are often retained well, and memory for a repeated event preserves what usually happened better than which details belonged to which occasion.

What it does not show: It does not show that episodic memory is generally untrustworthy, that a confident or detailed account is accurate, or that a confused or generic account is false. No behavioral test or brain scan can establish whether a particular remembered event happened as described.

The law: Expert testimony about episodic memory is governed by Rule 702 (amended 2023), Kumho, and Houser in courts-martial, and by Ariz. R. Evid. 702, Chapple, and Nordstrom in Arizona; experts may explain how memory works but may not opine on a witness’s credibility (Lindsey). Repeated-event memory also bears on charging and findings (Walters; A.R.S. § 13-1417; Klokic).

Issues for each side: Prosecutors can explain why a sincere witness to repeated abuse may describe what usually happened rather than each occasion, without treating a generic account as corroboration; defense counsel can examine where occasion-specific details, dates, and sources entered an account, without implying that confusion between occasions means nothing happened.

Episodic memory is memory for a specific event that a person experienced: what happened, where, and when. It is what a witness draws on to describe a particular night, conversation, or face, as distinct from general knowledge of facts and routines, and nearly every account of a disputed event rests in large part on it.

Episodic memory reaches court because the law usually asks about single occasions: a charge alleges an act on a date at a place. The research explains why people often answer such questions well, and also why they can err without lying, by forgetting a detail, attaching a correct detail to the wrong occasion, or adopting a detail learned afterward.

This paper covers the episodic–semantic distinction, how an event is linked to its context and source, consolidation and reconstruction, and memory for one occasion of a repeated event, a topic central to child abuse and intimate partner violence cases, followed by the limits of the research and the governing law. Memory for one’s own life and whereabouts, including alibis, is addressed in the companion paper, Autobiographical Memory.

Remembering and Knowing: Episodic and Semantic Memory

Tulving (1972) proposed dividing long-term declarative memory into two systems. Episodic memory holds personally experienced events located in time and place; semantic memory holds general knowledge, such as word meanings or the layout of a familiar building, without any record of when or where it was learned. Tulving later argued that episodic remembering carries a sense of mentally traveling back to the event, which he called autonoetic consciousness, while semantic knowing does not (Tulving, 1985, 2002); hence the shorthand of “remembering” versus “knowing.” Animal research on food-caching birds has found what researchers call episodic-like memory for what was stored, where, and how long ago (Clayton & Dickinson, 1998); it says nothing about how human witnesses perform.

The boundary between the two systems is less sharp than the original proposal suggested. Reviews of behavioral, neuropsychological, and imaging research conclude that episodic and semantic memory are closely intertwined, overlap substantially in the brain, and yet remain partly distinguishable (Renoult et al., 2019). A recent theoretical account places both along shared dimensions, such as whether a memory refers to oneself and whether it is tied to a specific scene, rather than treating them as separate boxes (Rubin, 2022).

The distinction matters in testimony because the two kinds of memory answer different questions. A witness who says she routinely checks her mirrors before changing lanes is describing a habit, which is generic knowledge; a witness who says she remembers a truck filling her mirror just before she changed lanes is claiming an episodic memory of one occasion. Both can be accurate. But a sincere witness asked about a particular night may answer from habit or general knowledge and experience the answer as a memory of that night (Lane & Houston, 2021, pp. 20–22). Asking whether the witness remembers a detail from that occasion or knows it is usually so is often more informative than asking whether the witness is sure.

Binding What, Where, When, and From Whom

Memory for an event does not work like a video file. The people, objects, and actions involved, and the place, time, and source surrounding them, are represented separately and have to be tied together when the event is experienced and tied together again when it is recalled. Research on recognition distinguishes recollection, retrieval of an item together with contextual details about the occasion, from familiarity, a feeling of prior encounter with no access to when or where it happened (Yonelinas, 2002). The two processes can come apart: a face, a phrase, or an object can feel familiar while the occasion on which it was encountered is lost.

The source monitoring framework describes how people decide where a remembered detail came from. Memories carry no label identifying their source; people infer the source from the features of the memory, such as its perceptual detail, its context, and the thoughts that accompanied it, and they can err when sources are similar, when encoding was weak, or when the judgment is made quickly (Johnson et al., 1993). Source errors are a principal route by which a detail heard from someone else or suggested by a question comes to be reported as part of the original experience.

Neuroscience has mapped much of this system. Regions of the medial temporal lobe support memory for items, memory for context, and the binding of the two, with the hippocampus central to linking an item to its context (Diana et al., 2007). After an operation that removed much of the medial temporal lobe on both sides, the patient H.M. could no longer form lasting new episodic memories, while much earlier knowledge was largely spared (Scoville & Milner, 1957). These findings explain episodic memory in general; they do not verify an individual memory. Imaging can detect average differences between true and false memories in laboratory tasks but cannot classify a particular witness’s memory (Lane & Houston, 2021, pp. 93–94).

Consolidation, Retrieval, and Reconstruction

Memory for an event continues to change after the event ends. In the hours and days afterward the memory is stabilized and reorganized, a process called consolidation, and sleep appears to play an active role in that process in human and animal studies (Diekelmann & Born, 2010). Retrieval is also an active process. Classic work showed that people retelling an unfamiliar story progressively reshaped it toward their own expectations (Bartlett, 1932), and modern accounts describe episodic memory as constructive: remembering assembles an account from stored fragments, general knowledge, and current cues, and the same flexibility that lets people imagine future events from pieces of past ones also allows elements from different sources to be combined in error (Schacter & Addis, 2007).

For these reasons, memory for peripheral details, specific dates, and the source of information is more error-prone in laboratory studies than memory for the gist and central features of an event. That conclusion has an important counterpart. Much of what people remember is accurate, especially the gist and central features of a distinctive event. One influential review of eyewitness identification research argued that a witness’s memory is generally reliable on an initial, uncontaminated test conducted with proper procedures, and that many errors arise from contamination and suggestive procedures after the event (Wixted et al., 2018). Research on consistency and accuracy has found that, in non-suggestive mock-crime studies, new details reported in a later interview were often accurate and that inconsistency between accounts, particularly the addition of details, is at best a weak indicator that the details are wrong (Fisher et al., 2009). Reconstruction therefore supports neither a presumption that accounts are unreliable nor one that confident accounts are accurate; it supports attention to what the person was exposed to between the event and each account.

One-Time Events and Repeated Events

Many cases involve a series of similar events, such as repeated abuse of a child or repeated incidents of partner violence, and memory for a series differs from memory for a single event. With repetition, people form a script, a general representation of what usually happens, that supports recall of the features shared across occasions; children as young as preschool age describe familiar events in generic, present-tense terms (what “happens”) and can have difficulty separating one occurrence from another (Hudson et al., 1992).

Experiments with children show both strengths and weaknesses in repeated-event memory. In one study, children who experienced an activity several times were more accurate and less affected by false suggestions about features that were the same every time than children who experienced it once; for features that changed from one occasion to the next, their memory of which version occurred on the target occasion declined, and most of their errors were details imported from other occasions rather than details that never happened (Powell et al., 1999). Whether repeated experience increases susceptibility to suggestion about a particular occasion has produced mixed findings, and later work suggests that it depends on how closely the changing details are related and on the child’s age (Connolly & Price, 2006). A review of this research concluded that children who have been abused repeatedly commonly provide script-like accounts and find it hard to attribute details to particular incidents, which creates tension with legal requirements to describe specific occasions (Roberts & Powell, 2001). Researchers have recommended interview methods that let children first describe what usually happened, then label and describe particular occasions, such as the first time, the last time, or a time that was different, without pressure to supply dates or counts the child does not know (Brubacher et al., 2014).

Adults show similar patterns. In an experiment in which some participants watched several similar distressing films, those participants later recalled the target film less accurately than participants who saw it alone (Theunissen et al., 2017). In a preregistered study prompted by the reporting demands placed on domestic violence complainants, women who imagined four instances of an abusive relationship or a non-abusive one remembered the last instance best, and the stressful scenario was remembered more accurately overall (Dilevski et al., 2022). An analysis of six studies found that confusions between instances are more frequent for middle instances than for the first and last, and occur most often between neighboring instances (Rubínová & Kontogianni, 2023). A 2026 experiment found that adults reported misleading information about one instance of a repeated event, especially when the misleading detail had appeared in a different instance, and that a general warning reduced the effect only on a recognition test (Smołka & Rubínová, 2026). Interviewing technique may help: instructing adults to mentally reinstate the context of a repeated activity increased the number of additional, unverifiable details they reported about particular occasions, although it did not change their reports of the checkable activity details (Sharman et al., 2022).

The practical implications cut in both directions. A generic account, an inability to give dates or counts, and placement of a detail on the wrong occasion are expected features of memory for repeated events and are not, by themselves, signs that the events did not occur. At the same time, the details most likely to be wrong are the occasion-specific ones: which detail happened when, on what date, and how many times. Those are often the details on which charges rest.

Limits of the Evidence

Most episodic memory research uses word lists, filmed events, or staged activities with students or children in low-stakes settings. Repeated-event studies typically involve a handful of occasions over days or weeks, not months or years of abuse or partner violence, and imagined or filmed abuse scenarios do not reproduce the fear and relationship dynamics of real victimization. Neuroscience findings are group averages from simple tasks, and some foundational work involves animals. A study can show that confusions between occasions become more likely under some conditions, not that a particular detail in a particular account was confused, and no research permits an expert to say that a particular witness’s memory is true or false.

Questions to Ask About This Research

When Powell et al. (1999) is cited to show that repeated experience protects memory, counsel should ask which details are at issue: the protection applied to features that stayed the same, not to which version of a changing detail occurred on a given occasion. When Dilevski et al. (2022) is offered to suggest that a complainant should remember the most recent incident best, counsel should ask who was studied and how the events were experienced: the participants were young women imagining four relationship instances over four weeks and tested one week later, not victims of real abuse recalling years of incidents. When Wixted et al. (2018) is cited for the reliability of an initial account, counsel should note that the review concerned eyewitness identification and ask whether the first account in this case was obtained before exposure to other information and with non-suggestive questioning. These questions are explained in “Reading Research Claims: A Guide for Attorneys” on this site.

Episodic Memory and the Law

Federal and Military Standards

The ordinary limits of episodic memory generally go to weight rather than competence. Expert testimony about episodic memory is governed by Federal Rule of Evidence 702, as amended December 1, 2023, under which the proponent must show the court that it is more likely than not that the rule’s requirements are met, including that the opinion reflects a reliable application of reliable methods to the case. Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993) made the judge a gatekeeper, and Kumho Tire Co. v. Carmichael (1999) extended that gatekeeping obligation to all expert testimony, including testimony based on technical or other specialized knowledge. In courts-martial, Military Rule of Evidence 702 tracks the federal rule; under Military Rule of Evidence 1102, the Joint Service Committee’s 2025 compilation reflects the 2023 amendment as part of the military rule (Joint Service Committee on Military Justice, 2025), and practitioners should confirm current text. Military judges also apply the six factors of United States v. Houser (1993).

Repeated-event memory also affects pleading and findings. Military specifications often allege acts “on divers occasions.” In United States v. Walters (2003), a drug-use case, the Court of Appeals for the Armed Forces held that when members except “divers occasions” and find the accused guilty of a single occasion, the findings must make clear which occasion, and it set aside an ambiguous finding; the court has applied the same rule to a specification alleging indecent acts with a child on divers occasions (United States v. Trew, 2010).

Arizona

Arizona Rule of Evidence 702 adopted the federal formulation and the Daubert standard effective January 1, 2012, and was amended effective January 1, 2024, to conform to the 2023 federal amendment (Ariz. Sup. Ct. Order R-23-0004). State v. Chapple (1983) is Arizona’s leading case on expert testimony about the reliability of memory: excluding a qualified eyewitness expert was an abuse of discretion on its facts, while admission generally remains discretionary, and State v. Nordstrom (2001) approved limiting such an expert to general factors without opinions on the accuracy of a particular witness. General, educational testimony that satisfies Rules 702 and 403 is permitted (State v. Salazar-Mercado, 2014), but experts may not opine on whether a particular witness is truthful or quantify how often complainants are truthful (State v. Lindsey, 1986, 149 Ariz. at 475–76; State v. Moran, 1986). For repeated sexual abuse of a child under fourteen, A.R.S. § 13-1417 requires proof of three or more qualifying acts over at least three months, and jurors must agree that the required number occurred without agreeing on which acts. When the State instead offers evidence of several acts to prove one charge, the court ordinarily must require an election or give a unanimity instruction unless the acts form a single criminal transaction (State v. Klokic, 2008).

Special Issues in Legal Practice

The principles described above apply with equal force to every party in a legal proceeding. The science operates the same way regardless of who is asking the questions, and the research summarized here does not by itself favor either side. What differs between the parties is not the science but the vantage point — the particular places where these issues tend to surface, and the particular errors each party is best positioned to guard against. The two summaries below identify those recurring issues. They are offered for orientation, not as litigation strategy; in every case the controlling question is what the evidence in that case will, and will not, support, and the expert’s role is to inform the trier of fact rather than to advocate for either side.

Special Issues for Prosecutors

The research supports several points prosecutors can legitimately present. The gist and central features of a distinctive event are often retained well, and, in non-suggestive mock-crime studies, details added in later interviews were often accurate. A witness to repeated abuse or partner violence may describe what usually happened, may be unable to give dates or counts, and may place a detail on the wrong occasion; general expert testimony can explain that these are expected features of repeated-event memory and not, by themselves, signs of fabrication. Prosecutors are well positioned to obtain and record an early account through open, non-leading questioning, to let witnesses label occasions in their own words, and to draft counts or specifications around the occasions an account actually distinguishes, such as the first or last time, or under A.R.S. § 13-1417 where its elements fit.

The research also counsels caution. Occasion-specific details, dates, durations, and counts are where repeated-event memory is weakest, and a charge that depends on a particular date or number may rest on the part of an account most open to error or suggestion. Testimony that treats a script-like account as confirming abuse goes beyond the research. Growing confidence or added detail after exposure to other accounts is not evidence that a memory is correct, and the distinction between a remembered occasion and an inference from habit applies to prosecution witnesses as much as to others.

Special Issues for Defense

The research supports several points defense counsel can legitimately present. Episodic memories are reconstructed, details can be borrowed from other occasions or later information through source errors, and familiarity can exist without memory of its source. In repeated-event cases, which version of a changing detail belongs to which occasion, and dates and counts, are the parts of an account most likely to be wrong, and suggestive questioning about a particular occasion can introduce details from another one. Defense counsel are well positioned to examine how each date, count, and occasion-specific detail entered the record, whether interviewers supplied labels or dates, and whether the charged acts match what the account supports, which bears on findings under Walters and unanimity under Klokic.

The research also counsels caution. Confusion between occasions, a generic account, or an inability to date events does not indicate that the events did not occur, and arguments that treat these features as signs of fabrication go beyond the research. Central features of distinctive events are often well retained, and a later-added detail is not presumptively false. An expert may describe the conditions under which source and occasion errors occur but may not tell the factfinder that a particular witness’s memory is mistaken (Lindsey; Nordstrom). The same mechanisms apply to an accused’s own account.

This paper is for educational purposes only and is not legal advice. The author is a psychologist, not an attorney; summaries of law are general and must be verified against current authority or with a licensed attorney.

References

Bartlett, F. C. (1932). Remembering: A study in experimental and social psychology. Cambridge University Press.

Brubacher, S. P., Powell, M. B., & Roberts, K. P. (2014). Recommendations for interviewing children about repeated experiences. Psychology, Public Policy, and Law, 20(3), 325–335. https://doi.org/10.1037/law0000011

Clayton, N. S., & Dickinson, A. (1998). Episodic-like memory during cache recovery by scrub jays. Nature, 395(6699), 272–274. https://doi.org/10.1038/26216

Connolly, D. A., & Price, H. L. (2006). Children’s suggestibility for an instance of a repeated event versus a unique event: The effect of degree of association between variable details. Journal of Experimental Child Psychology, 93(3), 207–223. https://doi.org/10.1016/j.jecp.2005.06.004

Diana, R. A., Yonelinas, A. P., & Ranganath, C. (2007). Imaging recollection and familiarity in the medial temporal lobe: A three-component model. Trends in Cognitive Sciences, 11(9), 379–386. https://doi.org/10.1016/j.tics.2007.08.001

Diekelmann, S., & Born, J. (2010). The memory function of sleep. Nature Reviews Neuroscience, 11(2), 114–126. https://doi.org/10.1038/nrn2762

Dilevski, N., Paterson, H. M., & van Golde, C. (2022). Adult memory for instances of emotionally stressful and non-stressful repeated events. Memory, 30(5), 621–635. https://doi.org/10.1080/09658211.2022.2038630

Fisher, R. P., Brewer, N., & Mitchell, G. (2009). The relation between consistency and accuracy of eyewitness testimony: Legal versus cognitive explanations. In R. Bull, T. Valentine, & T. Williamson (Eds.), Handbook of psychology of investigative interviewing (pp. 121–136). Wiley. https://doi.org/10.1002/9780470747599.ch8

Hudson, J. A., Fivush, R., & Kuebli, J. (1992). Scripts and episodes: The development of event memory. Applied Cognitive Psychology, 6(6), 483–505. https://doi.org/10.1002/acp.2350060604

Johnson, M. K., Hashtroudi, S., & Lindsay, D. S. (1993). Source monitoring. Psychological Bulletin, 114(1), 3–28. https://doi.org/10.1037/0033-2909.114.1.3

Joint Service Committee on Military Justice. (2025). Amendments to the Military Rules of Evidence since 1984 (G. E. Maggs, Ed.; 2025 ed.). https://jsc.defense.gov/Portals/99/MRE%20Amendments%202025.pdf

Lane, S. M., & Houston, K. A. (2021). Understanding eyewitness memory: Theory and applications. New York University Press.

Powell, M. B., Roberts, K. P., Ceci, S. J., & Hembrooke, H. (1999). The effects of repeated experience on children’s suggestibility. Developmental Psychology, 35(6), 1462–1477. https://doi.org/10.1037/0012-1649.35.6.1462

Renoult, L., Irish, M., Moscovitch, M., & Rugg, M. D. (2019). From knowing to remembering: The semantic–episodic distinction. Trends in Cognitive Sciences, 23(12), 1041–1057. https://doi.org/10.1016/j.tics.2019.09.008

Roberts, K. P., & Powell, M. B. (2001). Describing individual incidents of sexual abuse: A review of research on the effects of multiple sources of information on children’s reports. Child Abuse & Neglect, 25(12), 1643–1659. https://doi.org/10.1016/S0145-2134(01)00290-3

Rubin, D. C. (2022). A conceptual space for episodic and semantic memory. Memory & Cognition, 50(3), 464–477. https://doi.org/10.3758/s13421-021-01148-3

Rubínová, E., & Kontogianni, F. (2023). Sources and destinations of misattributions in recall of instances of repeated events. Memory & Cognition, 51(1), 188–202. https://doi.org/10.3758/s13421-022-01300-7

Schacter, D. L., & Addis, D. R. (2007). The cognitive neuroscience of constructive memory: Remembering the past and imagining the future. Philosophical Transactions of the Royal Society B: Biological Sciences, 362(1481), 773–786. https://doi.org/10.1098/rstb.2007.2087

Scoville, W. B., & Milner, B. (1957). Loss of recent memory after bilateral hippocampal lesions. Journal of Neurology, Neurosurgery, and Psychiatry, 20(1), 11–21. https://doi.org/10.1136/jnnp.20.1.11

Sharman, S. J., Danby, M. C., & Christopoulos, L. (2022). Mental context reinstatement improves adults’ reports of additional details from two instances of a repeated event. Memory, 30(8), 988–999. https://doi.org/10.1080/09658211.2022.2068610

Smołka, E., & Rubínová, E. (2026). Misinformation resistance in memory reports of one instance of a repeated event: Post-warnings reduce misinformation endorsement in recognition. Memory & Cognition. Advance online publication. https://doi.org/10.3758/s13421-026-01948-5

Theunissen, T. P. M., Meyer, T., Memon, A., & Weinsheimer, C. C. (2017). Adult eyewitness memory for single versus repeated traumatic events. Applied Cognitive Psychology, 31(2), 164–174. https://doi.org/10.1002/acp.3314

Tulving, E. (1972). Episodic and semantic memory. In E. Tulving & W. Donaldson (Eds.), Organization of memory (pp. 381–403). Academic Press.

Tulving, E. (1985). Memory and consciousness. Canadian Psychology, 26(1), 1–12. https://doi.org/10.1037/h0080017

Tulving, E. (2002). Episodic memory: From mind to brain. Annual Review of Psychology, 53, 1–25. https://doi.org/10.1146/annurev.psych.53.100901.135114

Wixted, J. T., Mickes, L., & Fisher, R. P. (2018). Rethinking the reliability of eyewitness memory. Perspectives on Psychological Science, 13(3), 324–335. https://doi.org/10.1177/1745691617734878

Yonelinas, A. P. (2002). The nature of recollection and familiarity: A review of 30 years of research. Journal of Memory and Language, 46(3), 441–517. https://doi.org/10.1006/jmla.2002.2864

Legal Authorities

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).

State v. Chapple, 135 Ariz. 281, 660 P.2d 1208 (1983).

State v. Klokic, 219 Ariz. 241, 196 P.3d 844 (App. 2008).

State v. Lindsey, 149 Ariz. 472, 720 P.2d 73 (1986).

State v. Moran, 151 Ariz. 378, 728 P.2d 248 (1986).

State v. Nordstrom, 200 Ariz. 229, 25 P.3d 717 (2001).

State v. Salazar-Mercado, 234 Ariz. 590, 325 P.3d 996 (2014).

United States v. Houser, 36 M.J. 392 (C.M.A. 1993).

United States v. Trew, 68 M.J. 364 (C.A.A.F. 2010).

United States v. Walters, 58 M.J. 391 (C.A.A.F. 2003).

Ariz. Rev. Stat. Ann. § 13-1417.

Fed. R. Evid. 702.

Mil. R. Evid. 702.

Mil. R. Evid. 1102.

Ariz. R. Evid. 702.

Ariz. Sup. Ct. Order R-23-0004 (amending Ariz. R. Evid. 702, effective Jan. 1, 2024).

Related topics from Arizona Forensic Services: Child Abuse Allegations · Courts-Martial