On Oct. 20, 1847, little William Nelman poisoned his grandpa. Who is this person and why did he do it? Why is it significant?

This appears to be a reference to the murder of Samuel Nelme by his grandson William Allnutt in England on October 20, 1847.

William, age 12, tended to be dishonest and often angered his grandfather. On one occasion, his grandfather hit William so hard that he fell down and knocked his head. Determined to have revenge, William stole arsenic (used to kill rats) and put it in the sugar bowl which his grandfather used liberally due to a sweet tooth. Even though William had ample opportunity over the next few days to reconsider this act and get rid of the arsenic, he did not and Samuel died about a week later.

This case was famous not only because it was shocking, but because the defense argued that William suffered from moral insanity -- that is, the part of his mind that knew what he was doing was not connecting to the part that knew murder to be wrong. Only 4 years earlier, the landmark McNaughton rule had defined the scope of the insanity defense. In his charge to the jury, the judge in this case attributed William's crime to "indulging habitually in a moody, resentful disposition" rather than true insanity, and instructed them that this was not a form of insanity that should relieve William of responsibility for his crime. The jury found William guilty.