He was tried along with Louisa Plant for the murder of their infant child Edward, in Macclesfield, through murder by arsenic poisoning. It was evidenced that Louisa had administered the poison, which she claimed was given to her by Thomas. The jury found Louisa Guilty of murder, with a reccomendation to mercy because of her age, and found Thomas not guilty of murder, but guilty of being an accessory. The judge stated that this was the same as an aquital, but that he should be tried as an accessory before the fact, which took place the following morning, and he was found guilty. Both were sentenced to death, although Louisa’s sentence was immediately commuted, and Thomas’ solicitor had raised legal objections, which led to him being transported for life.