As Lindsay Clancy’s murder trial ended on Friday, the Plymouth, Mass., courthouse was crowded. Her lawyer clashed with the judge, and a mistrial was narrowly avoided. The pivotal decision came behind closed doors: after nearly 40 hours of deliberation, half in deadlock, jurors couldn't agree unanimously on criminal responsibility for strangling her three children in 2023. One juror was at odds with the rest.

Hung juries are rare, says Valerie Hans, a Cornell law professor. "Maybe one out of every 20 cases in criminal courts results in a hung jury." Unanimity is required by the Sixth Amendment, affirmed in a 2020 Supreme Court decision. Christopher Slobogin of Vanderbilt University calls it "entirely an artifact of history and tradition."

Failures of consensus are most likely in close, complex cases. The Clancy trial fit: four weeks of emotional testimony, expert witnesses with opposite conclusions, and an insanity defense citing postpartum psychosis. The nine women and three men grew grim as deadlock persisted, even after Judge William Sullivan's "dynamite charge" on Wednesday. Slobogin noted such efforts usually succeed, but jurors said "with a heavy heart" they couldn't reach consensus.

Hans says jurors take their role seriously, often becoming more civically engaged afterward. The jurors' work is done, but Clancy still faces murder charges; prosecutors may retry the case with a new jury.