Throughout his life many friends, family members and eyewitnesses remarked that Isenschmid would act in strange and often violent ways suggesting an underlying mental illness. Sometime in 1882/83 his wife, Mary Ann Joyce, would claim that Jacob had a fit and that this was the cause of his strange behaviour. She also told the police during the Whitechapel investigation that Jacob would always carry a large knife with him. The locals nicknamed him the ‘Mad Pork Butcher’.
On the 11th September Dr Cowen of Landseer Road and Dr Crabb of Hollyway Road informed the police that a landlord by the name of George Tyler named Isenschmid as the Whitechapel murderer. Mr Tyler owned a lodge house on Milford Road where Isenschmid took up accommodation after splitting up with his wife. Tyler claimed that Isenschmid would often stay out all night and was absent on one particular night – the murder of Annie Chapman.
Crucially, an unusual incident occurred which potentially tied Isenschmid to the Chapman murder. A few moments after the murder Mrs Fiddymont, the landlady of the Prince Albert, encountered a ‘wild’ man with a torn and bloody shirt. Mrs Fiddymont’s pub was only 400 metres from the scene of Chapman’s murder. The suspect walked into the pub and purchased a drink before quickly leaving. Moments after the suspect met Joseph Taylor, a local builder, who followed the man for some time. Taylor remarked the individual’s ‘nervous and frightened way’ and noted that the man was holding his coat together at the top. Both Mrs Fiddymont and Joseph Taylor described a man matching the description of Jacob Isenschmid: early 40s, around 5’ 7” tall, curling ginger hair and a startled expression.
Isenschmid was arrested on the 12th September by Sgt William Thick and quickly declared insane by officials. He was eventually sent to Bow Infirmary Asylum on Fairfield Road, Bow. The key detective in the case, Detective Abberline, would later note that despite any solid evidence Isenschmid was a crucial suspect.