Conviction Reversed Because Bloodstain Expert Failed to Follow the Methodology He Defined as Reliable

Written on Saturday, February 22nd, 2020 by T.C. Kelly
Filed under: Expert Opinions, Working with Experts

In a case that achieved notoriety after CBS featured it on 48 Hours, the wife and father of a murder victim have been granted a new trial. The North Carolina Court of Appeals recognized that bloodstain evidence upon which the prosecution relied was insufficient to meet the state’s Daubert standard of admissibility.

The appellate court’s analysis is laudably thorough. Courts tend to be more careful about protecting the right to a fair trial in cases that have attracted the media’s attention. The decision makes clear that prosecution experts cannot ignore professional standards for rendering an opinion.

Facts of the Case

While living in Ireland, Jason Corbett hired Molly Martens to work as an au pair for his two children after his wife died. They began a romantic relationship and moved to North Carolina, where they married.

In 2015, Molly’s parents, Tom and Shannon, traveled from Tennessee to visit Jason and Molly. Tom is a retired FBI agent. On the first night of their visit, Tom woke up when he heard a scream. He grabbed a baseball bat and ran to Jason and Molly’s room, where he saw Jason choking Molly. When Jason saw Tom, Jason removed his hands from Molly’s neck and used his arm to place her in a chokehold.

Tom repeatedly told Jason to “let her go.” Jason replied, “I’m going to kill her.” Tom hit Jason with the bat repeatedly as Jason dragged Molly into a bathroom, back into the bedroom, and into the hallway. After Molly broke free, Jason and Tom struggled. Jason obtained possession of the bat after throwing Tom to the floor. As they renewed their struggle, Molly hit Jason with a brick paver.

Tom regained control of the bat. Fearing that Jason would attack again, Tom hit Jason with the bat until he was on the floor. He then called 911. Molly and Tom administered CPR to Jason until paramedics arrived. The paramedics determined that Jason had a hole in the back of his skull. Jason died from blunt force head trauma.

Jason and Molly’s two children told social workers that Jason had a history of abusing Molly. Because the children moved to Ireland before trial, the jury never heard their statements about Jason’s history of domestic violence.

Expert Evidence

Stuart James testified for the prosecution as an expert in bloodstain pattern analysis. In particular, he discussed stains on the bottom of Tom’s boxer shorts and the bottom of Molly’s pajama pants. James claimed the ability to discern that those stains were “impact spatters” of blood that came from Jason’s head when it was near the floor.

Proving that Jason’s head was near the floor was critical to the criminal charge. If Jason was struck while he was standing, the strikes were consistent with mutual combat and self-defense, not with a claim that Tom and Molly kept hitting Jason while he was down.

Prior to James’ testimony, a forensic scientist employed by the state crime lab testified about blood tests that the crime lab conducted on various items of evidence. He acknowledged that the stains about which James testified were never given a “presumptive” test to confirm the presence of blood. Not only did the crime lab fail to identify the stains as Corbett’s blood, it failed to identify the stains as blood at all.

James conceded on cross-examination that he didn’t really know whether the “blood spatter” he analyzed was actually blood. He also admitted that he did not know how Tom was wearing the boxer shorts. In particular, he did not know “whether the cuff was flipped up or down” or how the shorts laid on his body.

The defense challenged the reliability of James’ testimony. The defense pointed to a book that James had authored concerning blood spatter analysis, in which he stated that the presence of blood should be established to a scientific certainty as a predicate to rendering an admissible opinion.

The trial judge disposed of the Daubert challenge by asking James whether his testimony was based on reliable scientific principles. James said yes and that was good enough for the judge.

Jury Verdict

The jury convicted Molly and Tom of second-degree murder. North Carolina defines that crime as the unlawful killing of a human being with malice but without premeditation. Killing in self-defense is not unlawful, but the jury rejected the defense argument that Tom and Molly acted in self-defense.

Malice, under North Carolina law, refers to an intent to kill or to reckless conduct that is inherently dangerous and that exhibits an utter lack of regard for human life.

Appellate Analysis

North Carolina requires the trial judge to decide whether an expert is qualified to render an opinion and whether the opinion is both relevant and reliable. In 2016, the North Carolina Supreme Court concluded that the state’s rules of evidence require the reliability determination to be made in a manner that is consistent with the Daubert decision. Under that standard, expert opinions are reliable when they are based on sufficient facts, when they are the product of reliable principles and methods, and when those methods have been applied to the facts in a reliable way.

The defense did not challenge the reliability of blood spatter analysis in general, although such a challenge would have been well supported. A Pro Publica investigation found that courts have blindly accepted the testimony of self-proclaimed experts in blood spatter evidence despite the absence of any clear proof that the testimony is grounded in a reliable application of scientific principles.

The defense focused its challenge more narrowly on James’ assumption that the stains he analyzed were in fact Jason’s blood. James’ treatise on bloodstain analysis purports to define the standard governing the methodology for analyzing bloodstains. The treatise states that a visual identification of a substance as blood is inadequate. An analysis of a bloodstain should begin by confirming that the stain was caused by blood.

James did not follow the “proper scientific approach” that he identified in his own book. Failing to follow the methodology that James deemed essential to producing a reliable result undercut the reliability of his expert opinion.

James also testified that the “best practice” is to view a photograph of the person wearing the bloodstained clothing. A bloodstain analysis is affected by how the clothing fits the frame of the person wearing it. James saw no photograph of Tom wearing boxer shorts. He was therefore unable to determine the position of Tom’s body relative to Jason’s at the time of the alleged blood transfer.

The only photograph he saw of Molly wearing the pajama pants did not show how the pants fit. In that photograph, the pants seemed to be dragging on the floor. If Molly’s hems were touching the floor, it is difficult to understand how the blood could have come from Jason, given James’ opinion that blows to Jason’s head caused his blood to fly upward.

In the absence of testing confirming that the stains were actually caused by blood, James’ opinions were not based on sufficient facts or data. And since James did not follow the methodology he described in his treatise, he did not base his opinions on a reliable methodology. Given those circumstances, the court of appeals determined that James’ testimony should not have been admitted.

The testimony was important to the prosecution’s case. James did not claim that other blood stains on other articles of clothing were caused while Jason’s head was near the floor. The only testimony that allegedly supported the conclusion that Tom hit Jason while he was down involved the stains that were never tested and that might not have been blood, much less Jason’s blood.

Lesson Learned

In the end, James’ opinions were supported by speculation more than science. Speculation is not relevant evidence and it does not assist the jury in understanding the facts. Since improper speculation may have influenced the jury’s verdict — a verdict that seems to have been based entirely on James’ testimony, given that all the other evidence was consistent with self-defense — the court of appeals granted Tom and Molly a new trial.

If the case is retried, it might benefit the defense to call an expert witness who can explain why opinions about blood spatter are inherently unreliable. The large number of circumstances affecting the path that blood travels make it impossible to determine that path with certainty. A defense expert might explain how blood could have fallen from a higher point and landed on Tom’s boxer shorts. Whenever the prosecution calls an expert witness, it is helpful for the defense to call its own expert.


About T.C. Kelly

Prior to his retirement, T.C. Kelly handled litigation and appeals in state and federal courts across the Midwest. He focused his practice on criminal defense, personal injury, and employment law. He now writes about legal issues for a variety of publications.

About T.C. Kelly

Prior to his retirement, T.C. Kelly handled litigation and appeals in state and federal courts across the Midwest. He focused his practice on criminal defense, personal injury, and employment law. He now writes about legal issues for a variety of publications.