During the first several months of the investigation into the 1997 murder of Anastasia WitbolsFeugen, Kelly Moffett actively participated in a coverup of the murder, giving false statements to police on behalf of Byron Case, telling and sticking to a story that she and Case had agreed upon in a number of interviews with police. It was late 2000 when she became State's evidence after having admitted to a psychologist that she had witnessed the murder.

During the time that she was participating in the coverup, she took a VSA (Voice Stress Analysis) test¹ at the request of the investigating officer. The only known result of the test was that the test itself failed; whether it indicated her to be lying or telling the truth was never stated.

In pre-trial arguments of State v. Case, it was agreed that neither side would go into the fact that the VSA test had been given; however, she inadvertently mentioned it during her direct examination.²

Upon objection by defense counsel, several minutes of discussion were held outside the hearing of the jury, and some private discussion was held by Case and his counsel. The trial judge offered the defense a choice of asking for a mistrial or having the judge give a "cautionary instruction" to the jury. At the end of those discussions, it was agreed by all (including Case) that there would be no mistrial,³ and that the judge gave his instructions to the jury, as follows:

Ladies and gentlemen, I have an instruction I would like to give to you, and I would like you to listen to what I have to say very carefully, if you would.

There is no witness in this case that has ever taken any test with conclusive results regarding their truthfulness or untruthfulness.

Furthermore, such tests are deemed inadmissible and incompetent as evidence in state and federal courts throughout this country.

To consider any such evidence in this case for or against either side would be horribly unfair. For that reason, you should disregard any testimony regarding such evidence.⁴

In truth, the fact that a VSA had been taken could have been dangerous for both sides, and both defense and prosecution had reasons to avoid discussion of it.

In his 29.15 appeal, Byron Case, convicted killer, asserted that

[A]fter trial counsel objected to Moffett's testimony about the lie detector test, he and trial counsel went into a room outside of the courtroom to talk about the issue; that he told trial counsel that he wanted a mistrial. He told the Court that trial counsel was concerned about the witnesses' availability for the second trial; and that trial counsel never inquired of the witnesses to know whether they could return for another trial.

Case's counsel testified that

[H]e and his client discussed various concerns they had regarding the availability of witnesses, future trial dates and [defendant]'s desire to move forward with the case as soon as possible because he was in custody with a high bond; and that both he and Mr. Case discussed all the available options and decided together not to request a mistrial.

The Jackson County Circuit Court denied the appeal,⁵ as did both the Appellate and Missouri Supreme Courts.⁶

It could be inferred that Byron Case, believing that he was going to win acquittal, and wishing to not delay what he considered an inevitability, himself chose (or at the very least, agreed with his counsel) to forego being granted a mistrial.