Court Excludes Forensic Pathology Expert With History of Offering “Junk Science” Testimony

    Forensic Pathology Expert

    Court: Supreme Court of Wyoming
    Jurisdiction: Federal
    Case Name: Nielson v. State
    Citation: 2018 WY 132


    The appellant was found guilty of first-degree felony murder for causing the death of a 3-year old child. The child was admitted to a local emergency room following paramedic response to a 911 call by the appellant, who claimed that the child had jumped from a coffee table, hit a dollhouse, and fallen headfirst on the carpet before the dollhouse fell on him.

    The victim had been admitted in an unconscious state with a skull fracture, a subdural hematoma, and multiple broken ribs. One of his pupils was larger than the other, and his pupils were unresponsive to stimulation. He was referred to a children’s hospital where a team of expert pediatric professionals took care of him.

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    The appellant appealed against the judgment and his sentence, alleging error on the part of the district court in allowing testimony from a medical expert that opined on his guilt. He further alleged the court allowed improper cross-examination of his expert witness.

    The State’s Medical Expert Witness

    The state’s medical expert witnesses who had taken care of the victim during his treatment had concurred it was improbable that the subdural hematoma caused was caused by the accident as narrated by the appellant. These included a number of doctors who had treated the child, including a pediatric nurse and a forensic pathologist. They all opined that subdural hematomas are primarily caused by rapid acceleration and deceleration of the brain. These are commonly seen in children involved in high-speed car accidents or those who have suffered abusive trauma to the head.

    The Appellant’s Forensic Pathology Expert Witness

    The appellant called a certified forensic pathologist as an expert witness. The forensic psychology expert described the science on acceleration and deceleration injuries being the cause of subdural hematoma as a “hypothesis subject to a lot of controversy”. He cited a 2001 article in the American Journal of Forensic Medicine and Pathology by Dr. John Plunkett who had examined 18 cases where children suffered fatal injuries after falling short distances. He had also referred to another study which indicated that as little as a two-foot fall on the head can cause accelerations that reach lethal head injury threshold.

    On cross-examination, the expert testified that he had not performed an autopsy since 2011 and that he had not performed an autopsy on any 3-year-old child since before 2007. He had also not seen microscopic slides of the victim’s eyes and brain, prepared a medical report on his findings or consulted a forensic pathologist for this case. He had also agreed to the State’s question whether he made his money by “testifying and providing consultation”. The forensic pathology expert also testified that the Plunkett study was controversial, and that the cases it studied had differed from the victim’s.

    Court Discussion

    The appellant challenged the opinion of the state’s medical expert witness as “opining on the legal conclusion of his guilt, thus resulting in material prejudice”. The court dismissed this claim, noting that “the challenged expert testimony merely informed the jury about the meaning and significance”.

    The court also discussed the question of whether the district court had erred in the state’s cross-examination of the forensic psychology expert witness.

    The appellant had challenged the cross-examination, alleging two questions to be improper. The first being when the state had asked him about a District Court judgement in State of Kansas v. Jessica Dawn Harber finding his testimony “colored and not worthy of belief”, and the other where the state had asked about another case where he had been precluded from testifying after found using “junk science”. The appellant claimed that these questions de facto presented extrinsic evidence on a collateral matter, thus violating the “collateral evidence rule”. He alleged that these questions had caused material prejudice against him.

    The court noted that “Material prejudice results only when “there is a reasonable probability that the result would have been more favorable to the defendant had the error not occurred,” citing Larkins, 2018 WY 122, 94, 429 P.3d at 50.


    The court affirmed the district court’s decision, holding that the state’s medical experts had not offered improper testimony regarding the appellant’s guilt, but rather, provided expert inference of the cause of injury based on the presented symptoms. The court also held that the appellant had failed to prove that there was a reasonable probability that the outcome of the trial would have favored him more had the state not asked his forensic pathology expert the challenged questions.