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Hit – Smashed – Broken Glass

The Innocence Scholarship Column July 14, 2023


A previous column on eyewitness research, White Papers 2, noted that workable knowledge supporting lineup reforms is based on thousands of experiments conducted by hundreds of psychologists. Articles describing the experiments are published in peer-reviewed journals. Every research article is important. However, some are recognized as turning points.

One such article, published by Elizabeth Loftus and John Palmer in 1974, described two experiments in which subjects were shown a film of a multiple-car traffic accident. In the first experiment, after watching the film, some subjects were asked how fast the cars were going when they “hit” each other. Other subjects were asked how fast the cars were going using different verbs – when they smashed, collided, bumped, or contacted each other – in place of “hit.”


One result of the study was that estimates of speed increased as the verbs became more violent. The speed of the cars was the same in the film, but subjects asked about the cars smashing estimated speeds significantly faster than those asked about cars hitting each other.

In the second experiment, fifty subjects were asked how fast the car was going when the cars smashed into each other, fifty were asked how fast they were going when they hit each other, and fifty were not asked about speed. The film lasted less than a minute and the accident lasted four seconds. A week after watching the film the subjects were asked a set of questions, including whether they saw any broken glass.
There was no broken glass in the filmed accident.

A higher proportion of the subjects who were told that the cars smashed into each other said they saw broken glass compared to subjects told that the cars hit each other.
The experiment confirmed that the way a question is asked influences an answer. More significantly, Loftus and Palmer suggested that a memory consists of information from an initial event and external information. The two pieces of information merge to create one memory. Since higher speed is more consistent with broken glass, labeling the accident as a smash, caused the “memory representation” to shift toward being “more similar to a representation suggested by the verbal label.”

The implications of this study for the risks of misidentification were obvious. Elizabeth Loftus understood the process that created false memories of broken glass as witness contamination. Soon after, she began to apply her growing knowledge of memory error as an expert witness in a criminal case. After describing her research and expert testimony in a Psychology Today article (“Reconstructing Memory: The Incredible Eyewitness,” Spring 1975), she received calls from lawyers across the country. The broken glass experiment was described in her still-relevant 1979 book, Eyewitness Testimony, (republished in 1996). I would recommend the book to readers who want to get a deeper understanding of memory theory and its role in eyewitness identification.

By 1995 Loftus reviewed a raft of studies in a review article and concluded that “Nearly two decades of research on memory distortion leave no doubt that memory can be altered by a suggestion.”
Equally important, the research and the expert testimony of Loftus and fellow psychological scientists created a foundation for questioning established lineup practices conducted by even well-meaning police officers. As described in an earlier column, White Papers 1, this research helped to stimulate the innocence movement. When DNA exonerations were brought to light in the 1990s, proponents of change, like Attorney General Janet Reno, turned to the psychologists to supply scientifically-based techniques to reduce error in one critical area – lineup identifications.
The psychologists’ ideas seemed crazy to police and prosecutors when they first heard about it. Despite initial resistance, the powerful evidence provided by eyewitness research has revolutionized the way in which we think about criminal identification. Police are now willing to conduct lineups in accordance with psychological principles. To what extent this knowledge has influenced police practices and legislation will be the subject of a future column.

Copyright © 2023 Marvin Zalman

Editor's Note: Some excellent videos about witness contamination, including one by Elizabeth Loftus, can be viewed on our site here.



1 Comment


Bill Branham
Bill Branham
Jul 22, 2023

This shows how little we really know ourselves. The objective research by psychological scientists is incredibly important. Common sense can be deceiving. Thanks for explaining this!

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