Benjamin Geen is a double murderer who killed two patients and committed grievous bodily harm against 15 others while working as a nurse at Horton General Hospital in Banbury, Oxfordshire in 2003 and 2004. Geen was believed to be motivated by his 'thrill-seeking' temperament, and injected a number of patients with dangerous drugs in order to cause respiratory arrest so he could enjoy the 'thrill' of resuscitating them. He was apprehended after staff at the hospital noticed that it was always when he treated patients, most of whom only had minor injuries such as dislocated shoulders, that they inexplicably had respiratory failures. Upon his arrest, a syringe full of some of the drugs he used to attack patients was found on his person. When he saw officers approaching, he discharged the syringe contents into his jacket pocket in an attempt to hide the fact he had removed potentially lethal drugs from the hospital without authority. He was found guilty at trial in 2006 and sentenced to a minimum of 30 years imprisonment.

Geen has maintained his innocence but his multiple appeals have failed. Two applications for appeal to the Criminal Case Review Commission, the independent body which investigates alleged miscarriages of justice, have been rejected, most recently in 2020.