How a constipation defense resulted in a murder acquittal

On February 10th, 1843, a ferry docked in Camden; Mahlon Herberton was on the ferry when he was shot dead by Singleton Mercer.

Mercer killed Herberton because he had seduced and raped Mercer’s 16 year old sister, Sarah. Mercer was unable to prove to the authorities that the rape had happened so he went looking for Herberton. He followed his carriage to the ferry and shot him through the heart. He was immediately arrested and held without bail.

That’s when things got interesting. Public sentiment was overwhelmingly in favor of Mercer and he was tried only one month after his arrest. At this time the not guilty by reason of insanity defense was still relatively new and it was used by Mercer for the first time in New Jersey history. Of several reasons for his mental instability, one physician testified that “dreadful constipation” played a role.

The shock of his sister’s rape also played a role, driving Mercer to become “a foul mouthed hard drinking hysteric.” For whatever reason, the jury agreed and, after deliberating less than half an hour, returned the “not guilty” verdict. One lawyer, not involved in the case said “Mercer, the murderer has been acquitted by the leather-headed jackasses who were picked to try him.”

Mercer’s life after returning to Philadelphia was checkered at best, with citations for drunkenness and fighting. He died of yellow fever at age 35, ten years after his trial.

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