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Danger: Risk of contaminated false confessions

Guest post by Fabiana Alceste.

In 1994, a Washington, D.C. detective named James Trainum questioned a woman under suspicion of homicide. After a 16-hour interrogation, the woman relented and provided a detailed narrative of how she and two other men killed a man and threw him in the Anacostia River1. Her confession seemed perfect—she incriminated herself and included accurate and privileged information about the crime that only the police and the true perpetrator could have known.

After the confession, Trainum and his colleagues naturally considered the case closed. Although investigators could not find any other evidence against the suspect, her confession reinforced the investigators’ belief in her guilt – in part, because it contained those accurate details. Soon after, the investigation showed that it was impossible for this woman to have committed the crime—she had an ironclad alibi—and the charges against her were dropped. But how could she have possibly known the details of the murder so intimately if she did not commit the crime?

Years after the interrogation, Trainum and his colleagues revisited the videotape of her interrogation. Trainum watched himself as he asked the suspect leading questions, showed her the evidence collected by the police, and effectively, but unintentionally, taught the suspect precise details about the crime scene—the very details that were echoed in her confession and had calcified his belief in her guilt. He was watching the process of “contamination” that nearly put an innocent woman in prison.

The word “contamination” is commonly associated with events like chemical spills or an outbreak of E. coli on our supply of romaine lettuce. In criminal investigations, the word might make one think of keeping forensic materials in separate evidence bags so as not to mix the samples. But confessions can also be contaminated when suspects learn critical information about a crime through means other than guilty knowledge.

Generally speaking, confessions are pretty hard to disbelieve. If a significant other admits to lying about why they were late to a dinner date, you may be very likely to believe them…after all, why would they confess to something they didn’t do? In reality, false confessions are more prevalent than the average person may think. Data show that about 30% of DNA exonerations to date have included a false confession2. Importantly, though, false confessions contain much more than a bare “I did it” statement; analyses reveal that false confessions are usually convincing narratives, rife with accurate and nonpublic facts, such as visual descriptions of the crime scene, information about what the victim said, did, thought, and looked like, and details about location and time of the crime3.

The majority of false confessions contain details only the police and the true perpetrator should know.
For example, the false confession of Doug Warney—a DNA-exoneree who we now know to be factually innocent—included copious details about the murder and crime scene. His final statement described what the victim was wearing when he died; that he was cooking chicken in his house before he was killed; that the victim was stabbed multiple times with the murder weapon, which was a 12-inch serrated knife; and that there was a pornography tape in the television4. Yet another example is Jeffrey Deskovic’s multiple false statements about a murder he didn’t commit, which included drawings depicting multiple crime scenes, as well as specific descriptions of how the victim was struck, dragged, and suffocated. Warney and Deskovic are not outliers—one study showed that 71% of the analyzed false confessions included corroborated or nonpublic facts about the crime.

The fact that false confessions are often rich in details is dangerous for two reasons. First, research shows that detailed and narrative confessions are perceived as particularly convincing of guilt. Courts have even been known to cite the reliability of the details in a confession as a rationale for admitting it into evidence. Additionally, due in part to the presence of those details, it can be extremely difficult to identify a false confession as such5. Retrospectively knowing for a fact that exonerees like Warney and Deskovic did not perpetrate the crimes to which they confessed, there are only a few ways in which those privileged details could have ended up in his confession.

For example, a suspect’s knowledge of a crime might be contaminated if they hear about the crime on the news, talk to eyewitnesses or other suspects, and, of course, sit through an interrogation with loose-lipped detectives. During questioning, interrogators may, purposely or inadvertently, contaminate suspects’ knowledge of the crime by asking leading questions; correcting suspects’ incompatible descriptions of the crime, showing suspects photographs, maps, and other evidence in the investigation, and in some cases, even taking suspects to the crime scene and helping them reenact the event6. Of course, suspects may also guess the correct (or unverifiable) answers to questions about the crime, especially mundane or predictable details (Q: “What did she do when you chased her with the knife?”; A: “She screamed and tried to run away.”). But the greater the possibility of responses, the unusualness of the details, and the number of details, the lower the chance that a suspect’s guesses will be accurate7.

One critical way to detect if contamination has occurred is to do as Jim Trainum did and check the tape. A video-recording of the entire interview and interrogation process is the key to identifying whether the suspect introduced an important crime detail independently or if the interrogator revealed privileged information before the suspect admitted to knowing about it. Part of the transcript of a recorded false confession from the 1980s illustrates this crucial point:

Det. 2: Whatcha use [to tie her hands behind her back]?

Vasquez: The ropes?

Det. 2: No, not the ropes. Whatcha use?

Vasquez: Only my belt.

Det. 2: No, not your belt…Remember being out in the sunroom, the room that sits out to the back of the house?...and what did you cut down? To use?

Vasquez: That, uh, clothesline?

Det. 2: No, it wasn’t a clothesline... Think about the Venetian blinds, David.

Det. 2: (slamming his hand on the table and yelling) You hung her!

Vasquez: What?

Det. 2: You hung her!

Vasquez: Okay, so I hung her.

In this example, it is clear that Vasquez, another DNA exoneree, did not know how the victim died until the detective informed him. Without the recording of this exchange, we might never have come to know that the detective had contaminated Vasquez’s knowledge of the crime.

In a now-famous and widely publicized case out of Manitowoc, WI, a camera captured the process of contamination during the interrogation of a teenager named Brendan Dassey. Hours into questioning Brendan about a murder that police suspected his uncle of committing, interrogators grew frustrated with Brendan’s incorrect answers to their questions. After Brendan’s multiple incorrect guesses as to what was done to the victim, Teresa Halbach’s, head, an investigator finally leaked one of the only nonpublic details of the case when he asked, “Who shot her in the head?

If Brendan had independently volunteered information about the gunshot without any prompting from the police, that might reasonably be considered guilty knowledge. However, the moment the interrogator told Brendan, in the form of a question, that Halbach was shot, it became impossible to determine whether Brendan knew about the gunshot beforehand. The fact that this exchange and the rest of the interrogation was videotaped may be the difference between life in prison and a vacated conviction for Brendan. As of the time of this writing, Brendan is currently in prison on the sole basis of his confession, awaiting to hear whether the U.S. Supreme Court will review his case.

Brendan’s is not the first confession that has been publicly scrutinized for questionable interrogation practices. Investigators are indeed taught to avoid leading questions and contamination, but the interrogative process in the United States is a confrontational and guilt-presumptive one. American investigators are taught to instill in the suspect the sense that the police know everything about the crime, that it is futile to resist the accusation, and that the investigation has produced evidence that points to the suspect8.  This seems reasonably difficult to achieve without divulging some information about the crime—information that an innocent person would not know or likely be able to guess. Police usually open an interrogation with a positive direct confrontation (“Our investigation indicates that you were the one who shot Joe.”). Next, the interrogator engages in the process of “theme development”, a way to minimize the moral seriousness of the crime by offering face-saving excuses (“He was at the bar hustling you at pool. You lost a lot of money to him; it’s understandable that you reacted that way. I might have done the same thing myself.”). The interrogator may also lie about having incriminating evidence against the suspect (“Look, we found your fingerprints on the .38, so there’s no point in denying that you did this.”). By this time, an innocent person has already learned that the victim was (1) shot, (2) with a .38 caliber gun, (3) at a bar playing pool for money.

It may be the case that this confrontational interrogation style leads interrogators to be less careful when choosing the wording of their questions and avoid contamination because they believe the suspect already possesses guilty knowledge. After all, you can’t contaminate something that is already dirty.

Video recording interrogations can help assess whether a confession has been contaminated.
Since discovering that he inadvertently elicited a false confession, Jim Trainum has become a committed advocate for progressive, research-based interrogation practices that may decrease the risk of false or contaminated confessions. Such practices include adopting less confrontational and guilt-presumptive interrogation techniques, not relying on nonverbal behaviors as indicators of deception, and not lying to suspects about evidence. False confessions experts of the American Psychology-Law Society also strongly recommend the videorecording of custodial interrogations, which is currently mandated by around half of all states9.

Though this may be obvious, it bears pointing out that convicting an innocent person on the basis of a false confession actually constitutes two errors. First, an innocent person is wrongfully convicted—stripped of their rights, their reputation, and in the case of a false guilty plea, their right to appeal. The second error is that the guilty person goes free and in a lot of cases goes on to commit other crimes. Some people are confident enough to believe that they would be able to tell the difference between a true and false confession. I recommend thinking about it this way: All false confessions resulting in convictions have withstood the scrutiny of the criminal justice system—a system full of safeguards to prevent miscarriages of justice. This illustrates the pernicious effect of contamination, and it’s as good a reason as any to work toward preventing it and, if that fails, doing everything we can to identify it when it happens.

This post was written by Fabiana Alceste and edited by Timothy Luke and Will Crozier.


[1] Trainum, J. (2007). I took a false confession—So don’t tell me it doesn’t happen! The California Majority Report.


[3] Appleby, S. C., Hasel, L. E., & Kassin, S. M. (2013). Police-induced confessions: An empirical analysis of their content and impact. Psychology, Crime & Law, 19(2), 111-128.

[4] Garrett, B. L. (2010). The substance of false confessions. Stanford Law Review, 1051-1118.

[5] Kassin, S. M., Meissner, C. A., & Norwick, R. J. (2005). " I'd know a false confession if I saw one": a comparative study of college students and police investigators. Law and Human Behavior, 29(2), 211.

[6] Leo, R. A. (2013). Why interrogation contamination occurs. Ohio St. J. Crim. L., 11, 193.

[7] Ofshe, R. J., & Leo, R. A. (1996). The decision to confess falsely: Rational choice and irrational action. Denv. UL Rev., 74, 979.

[8] Inbau, F. E., Reid, J. E., Buckley, J. P., & Jayne, B. C. (2013). Criminal interrogation and confessions (5th ed.). Burlington, MA: Jones & Bartlett Learning.

[9] Kassin, S. M., Drizin, S. A., Grisso, T., Gudjonsson, G. H., Leo, R. A., & Redlich, A. D. (2010). Police-induced confessions: Risk factors and recommendations. Law and Human Behavior, 34(1), 3–38.

[10] Sullivan, T. P. (2016). States which record statewide. Unpublished document (prepared July 11, 2016).


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