The Polygraph-Induced Confession of Sandra Kemper

On 1 June 2006, Sandra Kemper was released from the St. Louis County, Missouri Justice Center after four-years of pre-trial detention, reports the St. Louis Post-Dispatch today in “Woman accused of killing son is set free,” by William C. Lhotka. Kemper had confessed to setting a fire that killed her 15-year-old son during a post-polygraph interrogation conducted by Detective Kenneth Schunzel, a polygraph operator with the St. Louis County Sheriff’s Office, who has since died. Schunzel told Kemper she had “failed” and conducted a lengthy post-test interrogation despite the fact, attested to by Dr. David Raskin, that by commonly accepted polygraph standards, she had clearly “passed.” Lhotka reports that Judge David Lee Vincent III, who heard evidence in the case, stated: “When I first saw the video evidence of the examination, I was shocked at the conduct of the polygraph examiner… He was using a polygraph as a guise to interrogate Mrs. Kemper.”

The Missouri Supreme Court summarized the case in a recent slip opinion:

About four months after her son was killed in a November 2001 fire at the family’s home, Sandra Kemper was taken into police custody and interrogated. She denied having any part in the fire initially and during a three-hour polygraph examination. Kemper was told the polygraph results had shown that she was lying about not being involved in the fire. She subsequently made two confessions, stating that she had planned the fire to obtain insurance payments and explaining how she had set the fire, although some of her statements were inconsistent with the physical evidence. The state charged Kemper with arson, first-degree murder and three counts of first-degree assault. In overruling a motion filed by the state, the trial court ruled that evidence of the polygraph could be admitted if the state attempted to introduce either of Kemper’s confessions. At trial, the state played for the jury Kemper’s two taped confessions as well as the administering detective’s statements that Kemper had failed the polygraph and that she had shown “signs of deception.” Because the court found that the state had opened the door to the polygraph results, the trial court permitted Kemper to present testimony from a polygraph expert who testified that Kemper had passed the polygraph and that the detective had misrepresented the results to her when he told her she had failed it. The next day, the trial court declared a mistrial on its own motion over Kemper’s objection, finding the admission of the polygraph results caused a manifest injustice. Kemper then moved to dismiss based on double jeopardy. The court overruled the motion and set the case for retrial, indicating that Kemper’s attorney exceeded the scope of its earlier orders by eliciting evidence of the polygraph results rather than just the fact that a polygraph had been taken. Kemper seeks a writ of prohibition from this Court.


Court en banc holds: (1) Generally, both the fact that a defendant took a polygraph and the results of the polygraph are inadmissible in Missouri criminal trials, and the parties may not stipulate to waive this inadmissibility. The polygraph test and its results are admissible here, however, because the state introduced Kemper’s confessions, which apparently were made in part because the detective incorrectly told Kemper she had failed the examination. As a result, they form the circumstances surrounding the confessions that are the basis of the state’s case. The credibility of Kemper’s confession is a matter for the jury, and evidence of the circumstances surrounding the confession is essential for the jury to assess credibility. In limited circumstances such as these, the state may not introduce a confession into evidence without polygraph evidence also being admissible.

(2) The Missouri constitution’s protection against double jeopardy does not bar Kemper’s retrial because it only applies to retrial after an acquittal. The federal constitution’s protection against double jeopardy, however, does bar the state from retrying Kemper because there was no manifest necessity requiring the trial court to declare a mistrial. Once her trial began, Kemper had the right to have her trial completed by the jury that had been selected. She did not request or consent to the mistrial. Rather, she objected strongly and offered a limiting instruction that would have instructed the jury how to consider the polygraph evidence. Considering all the circumstances, particularly the trial court’s earlier ruling that the polygraph results were relevant in evaluating Kemper’s confession, it appears the trial judge simply changed his mind, and so there was no manifest necessity.

This case is yet another that illustrates the importance of recording all custodial interrogations. Had the interrogation of Sandra Kemper not been videotaped, there would have been no objective record of what happened during the interrogation. For background on the Sandra Kemper case, see “Fire Proof” by Riverfront Times reporter Kristen Hinman.

Comments 2

  • I know this case well and Sandra Kemper is guilty. She murdered her 14 year old son and attempted to murder her husband and mother. It wasn’t the first fire she set. Interrogation tactics may not always be fair but she wasn’t physically or mentally coerced into a confession. Justice has not been served.

  • Her husband just confessed to a federal court that they both planned the arson for insurance money, presumably also planning the death of their son to get his life insurance payout in the process, since their “efforts” to save him do not seem to be what most parents would do in their situation.

    It looks like the late detective got a sound confession from a woman who murdered her son – who cares if he told her that she failed the polygraph test? Any parent who hadn’t done it would simply reply that the test was faulty or inaccurate rather than immediately confessing to their own son’s murder. The Missouri Supreme Court let a murderer go free on a technicality that doesn’t even stand up. What a miscarriage of justice for what seems like a very, very sweet 15-year-old boy.

    A polygraph result should not be used as evidence in court, but in this case, the defendant obviously thought the polygraph worked and did the job of the test herself, confessing her crimes. This is not an anti-polygraph story at all.

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