Although referred to as "insanity" in the story itself, Creeley's defense is actually called "non-insane automatism." This is a legal situation involving a case where a person has attacked or injured someone, but due to medical issues that have affected their mind, have been unable to properly form a motive - "mens rea" - for their actions against that person.
At the outset, the crime is stated as taking place on February 27, 1961. The train trip to the hospital with the now bedridden Creeley is supposed to be on August 9th, yet it is also described as "eleven months later".
Ironically enough, it is unlikely that Creeley would have been executed anyway due to reasons outside the scope of his trial. The last person to die in the electric chair in New York State was executed in 1963, and the state's death penalty was overturned by the Supreme Court in 1971. There was new legislation to revive the death penalty in 1995, but it was ruled unconstitutional in 2004 by the Supreme Court. Their death row was shut down in 2008, and thankfully, nobody else had been executed by that time; the intended method was lethal injection because Old Sparly, New York State's electric chair, had been scrapped after the 1971 Supreme Court ruling.