Previous research on how stereotypes affect perceptions of intimate partner violence and domestic homicide has found that violence committed by men is perceived as more severe and judged more harshly than violence committed by women. The present mock jury study investigated how perpetrator sex (male or female), crime type (familicide or filicide), and relatedness between perpetrator and child victims (biological or step) affect laypeople's perceptions of the appropriate consequence of the crime, the reason for the offense, responsibility of the perpetrator, the likelihood of certain background factors being present, and the risk of future violence. One hundred sixty-seven university students read eight fictive descriptions of cases of multiple-victim domestic homicides, in which the sex of the perpetrator, the crime type, and the relatedness between the perpetrator and the child victims were manipulated. We found that participants recommended equally severe punishments to and placed the same amount of responsibility on male and female offenders. Female offenders were, however, regarded as mentally ill to a larger extent and perceived more likely to have been victims of domestic violence compared with male offenders. Male offenders were seen as more likely to have committed domestic violence in the past, having been unemployed, have substance abuse, hold aggressive attitudes, and commit violent acts in the future. Participants also perceived offenders killing biological children as more mentally ill than those killing stepchildren. The present study extends the literature on the possible effect of stereotypes on decision making in psychiatric and judicial contexts.