Tawell fled the crime scene by train, but police were able to use the newly installed electric telegraph to circulate a description of the suspect ahead of his arrival at his destination, where he was identified as he left the station.

Tawell started out as a shop worker in London and for some years worked in a number of businesses owned by the Quakers, a strict religious society which he later joined.

However, the Quaker-owned bank was opposed to the death penalty and, mindful of scandal, negotiated for Tawell to be allowed to plead guilty to a lesser offence.

[2] After eventually obtaining his ticket of leave, Tawell prospered, opening the colony's first pharmacy and conducting numerous property and business ventures.

This secret relationship with Sarah Hart bore two children, and Tawell installed all three in a cottage in Salt Hill, one mile (1.5 kilometres) outside Slough[5] where he paid £1 per week to maintain them.

He bought two bottles of Scheele's prussic acid, a treatment for varicose veins containing hydrogen cyanide, and on 1 January 1845 travelled to Salt Hill, where he poisoned Sarah while sharing a beer in her cottage.

Following his trail, the police found that a person answering his description had caught the train at Slough, heading for Paddington Station in London.

Williams came back the following morning with Inspector Wiggins of the Metropolitan Police and they eventually arrested Tawell in a nearby coffee house.