Judging the sanity of criminal defendants is a difficult proposition for courts. Since the beginning of the Anglo-American criminal justice system, courts have struggled with just how to apply the medical issue of mental illness to the legal arena.

The issue of legal insanity was still relatively new when Nancy Farrer of Cincinnati, Ohio was put on trial in 1852 for committing a series of murders by poisoning.

Courts had first reckoned with insanity with the case of Daniel M’Naughten in 1843, after M’Naughten killed an employee of the British Prime Minister whom he thought was the leader of an outlandish plot against him. During his trial, witnesses testified to the fact that he was insane, and the jury acquitted him, finding him “not guilty by reason of insanity.”

The verdict caused a major brouhaha in England, and the House of Lords came up with a legal standard for determining the guilt of people who were obviously mentally ill.

The M’Naughten Rules, as they became known, essentially boil down to the belief that a defendant should not be held responsible for his actions if he could not tell that his actions were wrong at the time he committed them.

When Nancy Farrer went on trial, Ohio and many other states in the United States had not yet formally adopted the Rules.

In the early 1850s, Nancy Farrer, a nurse, was highly regarded by the patients she cared for, as well as by their families. It is clear from the record that while she was considered kind, the court held Nancy in low regard — with apparent good reason.

“There is full testimony to the effect, that in several households, Nancy, though awkward, and in many respects incapable, proved herself to be a kind and affectionate nurse,” the Ohio Supreme Court wrote in 1853. “She hardly ever spoke except when spoken to — asked no questions — never ran after company — readily did what she was bid.”

The court’s low regard for Nancy was partially based on the now-disproved “science” of phrenology — a system by which advocates believed a person’s intelligence, health and general psyche could be determined by the shape and character of the skull.

“In person, she is remarkably ugly,” the court wrote. “The eyes encroach on the space proper to the brain. Her head, in shape rather than size, is unfavorable to the usual presumption of sound mind and full capacity.”

Despite Justice Corwin’s reliance on Nancy’s appearance as proof of her insanity, there is significant other, more acceptable proof, that something was wrong with the girl.

“She had a notion of speaking back about it,” a friend, Mary Ann Dankey, testified at Nancy’s trial. “But she thought she’d fix her for it.”

Shortly after that exchange, Mrs. Forrest took ill after eating a supper Nancy prepared.

“Mrs. Forrest has been taken with vomiting and heaving, just like Mrs. Green,” Nancy told a member of the household, referring to a former employer who had also died.

While Mrs. Forrest lingered, and appeared to be recovering, another servant remarked that it was odd that the mistress of the house would take a turn for the worse after begining to recover. Again, Nancy referred to the late Mrs. Green.

“It was just the same way with Mrs. Green,” she replied. “Mrs. F. took to heaving just like Mrs. Green and I do not think she will recover.”

Mrs. Forrest did not recover and died the next day.

A week after Mrs. Forrest was buried, her son, John Edward Forrest took ill in the same fashion. He died shortly after he began vomiting a greenish bile.

After Johnny died, someone pointed out that Nancy was “unfortunate to live where so many people died.”

For the first time, the extent of Nancy’s murderous ways was made evident.

“Yes,” Nancy replied. “Five have died where I lived. First were Mrs. Green and her baby, and Mrs. Isherwood’s baby died a day or two after I left.”

Nancy predicted even more tragedy for the Forrest household.

“Jimmy will go next, and Billy, and the old man, and I expect they’ll all go of one complaint,” she said.

Then she tried to make light of the situation.

“How lucky I am with sick folks,” she said. “They all die.”

“Maybe you killed them,” Dankey replied.

“Maybe I did,” Nancy said.

Jimmy Forrest was Nancy’s next victim. Before he died, in fact, before he ever became ill, she predicted his demise to another witness.

“In a week or two, Jimmy will die,” she said.

Dankey pointed out that Jimmy was outside playing with other children and looked quite healthy. What did Nancy mean, the witness asked.

“I don’t know. Only he won’t eat,” she said.

Jimmy did get sick, vomiting green bile like his mother and brother. He died quickly, but not without considerable suffering. He claimed it was the “onion syrup” that Nancy was giving him that made him ill.

While Jimmy was in his sickbed, Nancy refused to eat dinner with the rest of the family, although that was her custom. That night, Elisha and Billy Forrest both became violently ill. They both recovered, however.

The number of deaths in the Forrest household, even in the 1850s when multiple deaths from mysterious illnesses was more common, prompted Elisha Forrest to ask that Jimmy’s corpse be autopsied.

A Dr. Dandridge conducted the post-mortem (in the Forrest home) and ruled that Jimmy had taken arsenic. He asked if Forrest had any rat poison around, to which Elisha replied no.

Dandridge would later testify that when poison was mentioned, Nancy became “quite excited and anxious.”

She refused to let Dandridge and Forrest discuss the matter outside her hearing and “if we were talking, she would walk up close to to wish to know what we were saying.”

The day after Jimmy’s funeral, Elisha Forrest found a paper outside Nancy’s room. It was wrapping paper bearing the label “Dr. Salter’s Drug Store.”

William Salter testified that about three weeks before the stomach of James Forest was brought to his brother to analyze, he sold Nancy five cents worth of arsenic, done up in a paper like that produced by Mr. Forrest. Nancy said she wanted it to kill rats.

Nancy’s Trial and the Aftermath

Unlike the trials of the current era that involve questions of sanity, there were no expert witnesses at Nancy’s trial to debate whether her actions were or were not those of a sane person. Instead, witnesses to her crimes were paraded before the jury which was then instructed — with erroneous instructions, Justice Corwin later wrote — about mental competency.

The trial court asked the jury to decide “Was Nancy Farrer, at the time this act was committed, capable of judging whether this act was right or wrong, and did she know at the time that it was an offence against the laws of God and man?

“So far as the girl Nancy is concerned, you will carefully examine the testimony, touching her knowledge of right and wrong, and if you find she was able to distinguish between them, then, no matter of how low an order may be her intellect, or how depraved her character, she is guilty as charged, if you have no reasonable doubt as to her commission of the act.”

Corwin wrote that this reliance on reasonable doubt as to Nancy’s sanity was the incorrect standard.

“The court characterized the old rule, requiring insanity to be proved beyond all reasonable doubt, as a doctrine, which though useful in its time, is too hard to uphold,” Corwin wrote. “And I cannot see that a reasonable doubt of a prisoner’s sanity can legally arise, except upon a preponderance of testimony.”

The jury did not find Nancy to be insane beyond a reasonable doubt, and although Corwin said he would have preferred an additional instruction about “irresistable impulse” (”The power of self-control — ‘free agency’ — is said to be quite as essential to criminal accountability as the power to distinguish between right and wrong”), had the jury not misbehaved in other ways, he would have let stand its verdict of guilty.

Fortunately for Nancy Farrer, the jury misconduct in her case gave Corwin the opportunity to toss out its verdict.

These errors, the court found, combined with the mistaken instructions on insanity, provided Corwin with sufficient grounds to overrule the jury verdict. He further ruled that it was clear that Nancy Farrer was insane and not criminally responsible for her actions.