Snap Shot
- The question: When a witness searches mug books, a computerized photo database, or social media before viewing a lineup, can that earlier viewing shape the later identification?
- What the research shows: Mug book searches can produce valid leads, though selections decline in long searches. In meta-analyses, prior mugshot exposure lowered later lineup accuracy and raised false identifications, especially when the witness had picked someone from the mugshots (a commitment effect). Studies of witnesses’ own online searches show harm in some conditions and none in others.
- What it does not show: Viewing unrelated photographs, with no face carried over to the lineup, did not significantly impair later identification of the culprit, and the research cannot show whether a particular witness’s identification was driven by memory of the crime or by an earlier photograph.
- The law: Simmons v. United States (1968) and Perry v. New Hampshire (2012) set the due process screen; Mil. R. Evid. 321 requires clear and convincing proof that an identification following an unreliable one is independent of it; Arizona tests pretrial identifications at a Dessureault hearing and instructs jurors under RAJI Standard Criminal 45.
- Issues for each side: Prosecutors should document every photograph a witness viewed and treat the first, uncontaminated identification as the probative one; defense counsel should trace the full viewing history, recognizing that exposure without overlap, and a first identification made under sound conditions, are not shown by the research to be unreliable.
When police have no suspect, they may ask a witness to look through photographs of people previously arrested, either in a printed mug book or on a computer screen, in the hope that the offender’s picture is among them. A mug book search differs from a lineup in purpose and design. A lineup tests whether one suspect is the offender by placing that person among known-innocent fillers. A mug book search has no suspect and no fillers; every face is a possible candidate, and the search may run to hundreds of photographs. Its purpose is to generate a lead, not to test one (Lindsay et al., 1994).
The search can matter later in a case. A witness who has studied many faces, and perhaps chosen one, may then view a lineup and later testify. If the same face appears at more than one stage, the question becomes whether the witness is recognizing the offender or a face seen during the investigation. The same question arises when witnesses search social media on their own. This paper reviews the research on these issues, its limits, and the governing federal, military, and Arizona law.
Searching Mug Books and Photo Databases
In three staged-crime experiments with 365 participants, witnesses who searched mug shots frequently selected the confederate who had committed the staged crime, and few selected innocent people, which supports the use of mug books as an investigative tool (Lindsay et al., 1994). The same studies identified conditions that reduce a search’s value. Selections declined as the number of photographs viewed before the culprit’s increased. Biased instructions, clothing resembling the offender’s, and sorting photographs to match the witness’s description increased selections of innocent people.
Many agencies now search computerized databases that can be filtered by description or ranked by a face-matching algorithm. In a study of a 208-photograph computerized mug book, false identifications were significantly higher when photographs were shown one at a time than twelve to a page, the reverse of what lineup research might predict (Stewart & McAllister, 2001). Procedures that help in lineups do not automatically transfer to mug books, and a search that surfaces faces resembling the description raises the chance of encountering an innocent lookalike.
Mugshot Exposure and Later Lineups
Two meta-analyses combined 32 independent tests of whether prior mugshot exposure lowers accuracy at a later lineup (Deffenbacher et al., 2006). Across those tests, mugshot exposure significantly reduced the proportion of correct identifications and increased false identifications, with the larger effect on false identifications. Whether the witness had identified someone from the mugshots was a substantial moderator of both effects. Simple retroactive interference, in which the culprit was not among the mugshots and no one from the mugshots reappeared at the lineup, did not significantly impair identification of the culprit. Viewing unrelated faces was not shown to erode the original memory; the risk arose mainly when faces carried over from one procedure to the next.
In the classic experiments, participants who saw faces only in mugshots sometimes identified those people in a later lineup as having been present at the original event (Brown et al., 1977). Witnesses who chose an incorrect photograph were later drawn back to that same person (Gorenstein & Ellsworth, 1980), and witnesses who had committed to a mugshot made fewer correct identifications of the actual culprit afterward (Brigham & Cairns, 1988). In live staged-crime experiments, mug shots did not change correct decision rates when no face carried over, but witnesses who had chosen someone from them later made significantly more false identifications than controls (Dysart et al., 2001). Witnesses who picked someone from innocent mugshots that included a critical foil later chose that foil at inflated rates from a culprit-absent lineup, despite context reinstatement instructions (Memon et al., 2002).
Commitment, Familiarity, and Source Confusion
Researchers have proposed two main explanations for mugshot exposure effects. Under a commitment account, a witness who has chosen a face tends to stay with that choice, whether from a wish to be consistent or because the act of choosing strengthens the memory of that face. Under a familiarity or source-confusion account, which requires no earlier choice, a face seen before feels familiar later, and the witness may credit that familiarity to the offense instead of the photograph. The same error underlies unconscious transference, the mistaken identification as the offender of someone seen in an unrelated, innocent setting. In a third meta-analysis of 19 tests of transference, the effect was more than twice as large in studies in which mugshot exposure occurred close in time to the target than in “bystander” studies with no later mugshot exposure (Deffenbacher et al., 2006); the Unconscious Transference paper addresses that phenomenon. Within a dual-process view of recognition, familiarity without recollection of where a face was seen is an unsafe basis for an identification (Lane & Houston, 2021, pp. 48–51, 54).
Commitment, familiarity, and source misattribution are not mutually exclusive mechanisms, and the evidence on which predominates generally favors commitment. After a 50-photograph mug book without the culprit, witnesses who chose someone tended to select that person from a later lineup or, when that person was absent, to reject a lineup containing the actual culprit, while non-choosers tended to reject the lineup; the authors attributed most errors to commitment to a prior selection or decision strategy (Goodsell et al., 2009). Dysart et al. (2001) likewise found a commitment effect but no transference effect, whereas Memon et al. (2002) discussed both commitment and source memory. The mechanisms are not mutually exclusive, and because studies differ in mug book size, delay, and procedure, the contribution of familiarity remains unsettled.
Repeated Identification Procedures
The concern about mug books is one instance of a broader problem: repeated identification procedures with the same witness and suspect. A witness who has chosen someone once tends to choose that person again in a later procedure (Deffenbacher et al., 2006; Steblay & Dysart, 2016). In 2020, a scientific review paper commissioned by the American Psychology-Law Society issued nine recommendations for identification procedures, among them a new recommendation to avoid repeated identification attempts with the same witness and the same suspect (Wells et al., 2020; see Lane & Houston, 2021, pp. 152–153).
Wixted et al. (2021) explained the rationale: a lineup leaves a memory trace of its faces, so on a later test the suspect’s face generates a stronger memory signal even if the suspect is innocent; testing memory can contaminate memory. The authors noted that many witnesses who identified a defendant with high confidence in court had initially identified the suspect with low confidence or not at all, and they argued that the recommendation applies to the in-court identification as well. The reasoning applies to mug books: once a witness has seen, and especially chosen, a face in a search, a later lineup including that face retests a memory already changed. A second selection of the same person is therefore not an independent test of memory.
The same research supports the value of the first test. Under proper procedures, an initial, uncontaminated identification, particularly one made with high confidence, carries substantial information about accuracy, while later identifications and later confidence carry less (Wixted et al., 2018). A first identification from a database search can therefore be informative, depending on the length of the search, how photographs were selected, the instructions, and whether confidence was recorded at the time.
Online and Self-Directed Searches
Witnesses now sometimes search for a culprit on their own, on social media or news sites, before police conduct any procedure. In an online study of 285 participants, those who saw a lookalike of the culprit on a mock social media page were about 30% more likely than others to fail to identify the culprit in a culprit-present lineup a week later, with no significant effect in culprit-absent lineups (Elphick et al., 2021). In a similar design using video lineups, social media exposure had no detectable effect in culprit-present lineups, and in culprit-absent lineups the only significant difference was more correct rejections among witnesses who had seen the actual culprit online (Havard et al., 2023).
A third study compared online images with a police mug book. Seeing an innocent suspect’s image on social media increased misidentification of that person in both experiments, while a mug book did so only in the second, after the innocent suspect had been made a more plausible culprit (Kruisselbrink et al., 2023). Exposure to either source also reduced the accuracy of high-confidence identifications, weakening the confidence-accuracy relationship. Together, these studies suggest that online exposure can contaminate a later identification under some conditions; the evidence is still limited.
Limits of the Evidence
Most mug book research uses students or online participants viewing staged or filmed events, with low stakes and delays of up to about a week; real searches may involve longer delays, larger databases, and emotionally significant events. Many classic studies are decades old and used small printed mug books, while computerized databases and algorithmic ranking have been studied far less. The meta-analytic effects are averages across varied designs; the commitment effect has been consistent, the familiarity effect less so. The social media studies are recent, few in number, and not fully consistent. Group research describes how procedures change identification rates across many witnesses; it cannot determine whether a particular witness’s identification reflects memory of the offender or memory of a photograph.
Questions to Ask About This Research
When the meta-analytic finding that mugshot exposure impairs later identification is cited, counsel should ask whether any face actually carried over from the search to the lineup and whether the witness chose anyone, because Deffenbacher et al. (2006) found no significant impairment without overlap and found that choosing moderated the effects. When a lineup identification is offered as confirming an earlier database pick of the same person, counsel should ask what the second procedure could add, given that Wixted et al. (2021) and Wells et al. (2020) treat repeated testing as a source of contamination, and should examine the conditions of the first pick.
When the social media studies are cited, counsel should ask which one and under what conditions, since Elphick et al. (2021) and Kruisselbrink et al. (2023) found harm in some conditions while Havard et al. (2023) did not. Counsel may also ask what this witness saw online, when, and whether any record exists. These questions are explained in “Reading Research Claims: A Guide for Attorneys” on this site.
Mugshot Exposure and the Law
Federal and Military Standards
In Simmons v. United States (1968), the Supreme Court declined to prohibit photographic identification and held that an identification following a pretrial photographic display will be set aside on that ground only if the procedure was so impermissibly suggestive as to give rise to a very substantial likelihood of irreparable misidentification. The Court observed that improper use of photographs can lead witnesses to err, that a witness may afterward retain the image of the photograph rather than of the person actually seen, and that the danger increases when only one person’s photograph is shown or when one person’s photograph recurs or is emphasized (390 U.S. at 383–84). Foster v. California (1969) found a due process violation where the defendant was the only person repeated across lineups after a one-on-one confrontation. Neil v. Biggers (1972) and Manson v. Brathwaite (1977) make reliability the controlling question, and Perry v. New Hampshire (2012) limited the due process screen to suggestive circumstances arranged by law enforcement, so a witness’s own online search is generally tested through cross-examination, instructions, and expert testimony; some states have revised their frameworks (State v. Henderson, N.J. 2011). Expert testimony is governed by Federal Rule of Evidence 702, as amended December 1, 2023, Daubert v. Merrell Dow Pharmaceuticals, Inc. (1993), and Kumho Tire Co. v. Carmichael (1999), which extended gatekeeping to all expert testimony.
In courts-martial, Military Rule of Evidence 321 governs identification evidence. An identification of the accused is inadmissible, on timely motion or objection, if it results from an unlawful lineup or other identification process conducted by the United States or other domestic authorities, or if due process requires exclusion; a process is unreliable, and therefore unlawful, if it is so suggestive as to create a substantial likelihood of misidentification (Mil. R. Evid. 321(b), (c)(1)). When the military judge finds an identification was the result of an unreliable one, a later identification may be admitted only if the prosecution proves by clear and convincing evidence that it is not the result of the inadmissible identification (Mil. R. Evid. 321(d)(6)(B)(ii)), a standard that bears directly on a lineup or in-court identification following a suggestive photographic display; prior identifications must be disclosed before arraignment (Mil. R. Evid. 321(d)(1)). In United States v. Garcia (1996), the military judge excluded a defense expert’s testimony on an “inverse” relationship between confidence and accuracy and on memory transference and transposition; the Air Force Court of Military Review found an abuse of discretion but no prejudice, and the Court of Appeals for the Armed Forces affirmed, holding any error harmless beyond a reasonable doubt (44 M.J. at 28–31, 33); later research has found that the confidence-accuracy relationship depends on the conditions of the identification (Wixted et al., 2018). Expert testimony is assessed under Military Rule of Evidence 702 and United States v. Houser (1993); under Military Rule of Evidence 1102, the 2023 federal amendment to Rule 702 became part of the military rule in 2025 (Joint Service Committee on Military Justice, 2025), and practitioners should confirm current text.
Arizona
A defendant who challenges a pretrial identification in Arizona may obtain a hearing outside the jury’s presence under State v. Dessureault (1969); if the pretrial procedure was unduly suggestive, the State must show by clear and convincing evidence that the in-court identification is not tainted by it. Arizona’s standard instruction on identification (RAJI Standard Criminal 45, formerly No. 39) tells jurors that the State must prove beyond a reasonable doubt that the in-court identification is reliable, lists factors drawn from Biggers, including certainty at the pretrial identification, and permits consideration of any other factor affecting reliability, under which earlier exposure to the defendant’s photograph may be argued. State v. Chapple (1983), Arizona’s leading case on eyewitness expert testimony, held that excluding such testimony was an abuse of discretion on the facts of that case; admission otherwise remains within the trial court’s discretion (State v. Nordstrom, 2001). Arizona Rule of Evidence 702 adopted the Daubert standard effective January 1, 2012, and was amended effective January 1, 2024, to track the 2023 federal amendment (Ariz. Sup. Ct. Order R-23-0004). No published Arizona decision on mugshot commitment as such was confirmed for this paper.
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 propositions prosecutors can legitimately present. Mug book and database searches can produce accurate leads. Viewing unrelated photographs did not significantly impair later identification of the culprit, so the fact that a witness looked through mug shots does not by itself make a later identification unreliable. A first identification made under sound conditions, with confidence recorded at the time, can be informative, and one of three studies found no detectable harm from witnesses’ own social media searches, while the other two found harm under some conditions. Prosecutors can protect that evidence by ensuring that investigators record which photographs a witness viewed, how they were selected, the instructions, any choice, the witness’s words of confidence, and anything seen online.
The research also counsels caution. When a witness picked someone from a mug book or database and later identified that same person in a lineup and in court, the later identifications are not independent corroboration, and presenting them as such goes beyond what the research supports. An innocent person seen or chosen during a search is at elevated risk of later identification, and repeated procedures with the same witness and suspect are what the 2020 recommendations advise against; confidence that grows across procedures is a weak indicator of accuracy.
Special Issues for Defense
The research supports several propositions defense counsel can legitimately present. Prior mugshot exposure lowered later lineup accuracy and raised false identifications in meta-analyses, particularly when the witness had chosen someone; a witness who committed to a face tends to choose it again, and familiarity from a photograph can be mistaken for memory of the event. Repeated testing can strengthen memory of a suspect’s face whether or not the suspect is guilty, and confidence at trial can exceed confidence at the first procedure. The full viewing history, including online searching, and, where admissible, expert testimony on these effects can help the factfinder evaluate an identification.
The research also counsels caution. Exposure to photographs with no face carried over to the lineup was not shown to impair later identification, and a witness who first picked the defendant from a properly conducted search may have picked the culprit; the commitment research explains why later identifications add little, not why the first one was wrong. The familiarity effect has been inconsistent, and the social media research is mixed. An expert can describe how mugshot exposure affects identifications in general but cannot tell the factfinder that a particular witness identified the defendant from a photograph rather than from memory of the event.
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
Brigham, J. C., & Cairns, D. L. (1988). The effect of mugshot inspections on eyewitness identification accuracy. Journal of Applied Social Psychology, 18(16), 1394–1410. https://doi.org/10.1111/j.1559-1816.1988.tb01214.x
Brown, E., Deffenbacher, K., & Sturgill, W. (1977). Memory for faces and the circumstances of encounter. Journal of Applied Psychology, 62(3), 311–318. https://doi.org/10.1037/0021-9010.62.3.311
Deffenbacher, K. A., Bornstein, B. H., & Penrod, S. D. (2006). Mugshot exposure effects: Retroactive interference, mugshot commitment, source confusion, and unconscious transference. Law and Human Behavior, 30(3), 287–307. https://doi.org/10.1007/s10979-006-9008-1
Dysart, J. E., Lindsay, R. C. L., Hammond, R., & Dupuis, P. (2001). Mug shot exposure prior to lineup identification: Interference, transference, and commitment effects. Journal of Applied Psychology, 86(6), 1280–1284. https://doi.org/10.1037/0021-9010.86.6.1280
Elphick, C., Philpot, R., Zhang, M., Stuart, A., Pike, G., Strathie, A., Havard, C., Walkington, Z., Frumkin, L. A., Levine, M., Price, B. A., Bandara, A. K., & Nuseibeh, B. (2021). Digital detectives: Websleuthing reduces eyewitness identification accuracy in police lineups. Frontiers in Psychology, 12, Article 640513. https://doi.org/10.3389/fpsyg.2021.640513
Goodsell, C. A., Neuschatz, J. S., & Gronlund, S. D. (2009). Effects of mugshot commitment on lineup performance in young and older adults. Applied Cognitive Psychology, 23(6), 788–803. https://doi.org/10.1002/acp.1512
Gorenstein, G. W., & Ellsworth, P. C. (1980). Effect of choosing an incorrect photograph on a later identification by an eyewitness. Journal of Applied Psychology, 65(5), 616–622. https://doi.org/10.1037/0021-9010.65.5.616
Havard, C., Strathie, A., Pike, G., Walkington, Z., Ness, H., & Harrison, V. (2023). From witness to web sleuth: Does citizen enquiry on social media affect formal eyewitness identification procedures? Journal of Police and Criminal Psychology, 38(2), 309–317. https://doi.org/10.1007/s11896-021-09444-z
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
Kruisselbrink, E. D., Fitzgerald, R. J., & Bernstein, D. M. (2023). The impact of viewing social media images on eyewitness identification. Psychology, Public Policy, and Law, 29(4), 457–470. https://doi.org/10.1037/law0000401
Lane, S. M., & Houston, K. A. (2021). Understanding eyewitness memory: Theory and applications. New York University Press.
Lindsay, R. C. L., Nosworthy, G. J., Martin, R., & Martynuck, C. (1994). Using mug shots to find suspects. Journal of Applied Psychology, 79(1), 121–130. https://doi.org/10.1037/0021-9010.79.1.121
Memon, A., Hope, L., Bartlett, J., & Bull, R. (2002). Eyewitness recognition errors: The effects of mugshot viewing and choosing in young and old adults. Memory & Cognition, 30(8), 1219–1227. https://doi.org/10.3758/BF03213404
Steblay, N. K., & Dysart, J. E. (2016). Repeated eyewitness identification procedures with the same suspect. Journal of Applied Research in Memory and Cognition, 5(3), 284–289. https://doi.org/10.1016/j.jarmac.2016.06.010
Stewart, H. A., & McAllister, H. A. (2001). One-at-a-time versus grouped presentation of mug book pictures: Some surprising results. Journal of Applied Psychology, 86(6), 1300–1305. https://doi.org/10.1037/0021-9010.86.6.1300
Wells, G. L., Kovera, M. B., Douglass, A. B., Brewer, N., Meissner, C. A., & Wixted, J. T. (2020). Policy and procedure recommendations for the collection and preservation of eyewitness identification evidence. Law and Human Behavior, 44(1), 3–36. https://doi.org/10.1037/lhb0000359
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Wixted, J. T., Wells, G. L., Loftus, E. F., & Garrett, B. L. (2021). Test a witness’s memory of a suspect only once. Psychological Science in the Public Interest, 22(1, Suppl.), 1S–18S. https://doi.org/10.1177/15291006211026259
Legal Authorities
Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).
Foster v. California, 394 U.S. 440 (1969).
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999).
Manson v. Brathwaite, 432 U.S. 98 (1977).
Neil v. Biggers, 409 U.S. 188 (1972).
Perry v. New Hampshire, 565 U.S. 228 (2012).
Simmons v. United States, 390 U.S. 377 (1968).
State v. Chapple, 135 Ariz. 281, 660 P.2d 1208 (1983).
State v. Dessureault, 104 Ariz. 380, 453 P.2d 951 (1969).
State v. Henderson, 208 N.J. 208, 27 A.3d 872 (2011).
State v. Nordstrom, 200 Ariz. 229, 25 P.3d 717 (2001).
United States v. Garcia, 44 M.J. 27 (C.A.A.F. 1996).
United States v. Houser, 36 M.J. 392 (C.M.A. 1993).
Fed. R. Evid. 702.
Ariz. R. Evid. 702.
Ariz. Sup. Ct. Order R-23-0004 (2023) (amending Ariz. R. Evid. 702, effective Jan. 1, 2024).
Mil. R. Evid. 321.
Mil. R. Evid. 702.
Mil. R. Evid. 1102.
Revised Arizona Jury Instructions (Criminal), Standard Criminal 45 (Identification) (State Bar of Arizona 2022).
Related topic papers: Unconscious Transference · Lineup Construction · Confidence and Accuracy · Improving Eyewitness Memory · Source Monitoring · Face Recognition
Related topics from Arizona Forensic Services: Courts-Martial