At the Massachusetts murder trial of Lindsay Clancy, the woman accused of killing her three young children, prosecutors questioned her devoutly Catholic mother-in-law, Susan Clancy, about whether she understood murder to be a "mortal sin". The question was intended to support the prosecution's argument that Clancy understood the wrongfulness of her actions at the time of the killings, directly challenging the defence's case that she was suffering from severe postpartum psychosis and therefore lacked criminal responsibility.

The line of questioning prompted the judge to immediately call a sidebar conference, reflecting its sensitivity and potential legal significance to the case. The trial centres on competing accounts of Clancy's mental state: prosecutors are seeking to establish that she knowingly committed the killings, while her defence team maintains that a severe episode of postpartum psychosis drove her actions, a claim that, if accepted, could affect her criminal culpability.