Rossum

State prisoner Kristin Rossum appeals the district court’s denial of her petition for a writ of habeas corpus. We reverse and remand for the district court to hold an evidentiary hearing on Rossum’s claim that she was deprived of her Sixth Amendment right to the effective assistance of counsel.

Rossum was convicted of murdering her husband, Gregory de Villers. The prosecution’s theory of the case was that Rossum poisoned de Villers using fentanyl, a powerful synthetic opiate. Rossum contends that her counsel rendered ineffective assistance by failing to have de Villers’s autopsy samples tested for fentanyl metabolites, a test that would have resolved whether de Villers had in fact ingested fentanyl or whether fentanyl found in the samples was a product of laboratory contamination subsequent to his death. Rather than investigating, Rossum’s counsel simply conceded that the cause of death was fentanyl.

The prosecution’s case was purely circumstantial, hinging in large measure on toxicological and medical evidence which was equivocal. The fentanyl levels in de Villers’s autopsy samples were extraordinarily, even unnaturally, high. While these elevated concentration levels…