Gregory Davis was born in 1979 in Great Linford, Buckinghamshire, England. He was the son of a civil engineer and a care assistant. Davis attended The Radcliffe School and later pursued art studies during his sixth form and at Northampton University. During this period, he created a trophy plaque bearing the names of his favorite serial killers, indicating a disturbing fascination with such figures. ​

On January 28, 2003, Davis embarked on a planned killing spree, targeting individuals listed in his diary. His first intended victim, Stewart Johnson, escaped unharmed due to the presence of workers in his home. Davis then proceeded to the home of Dorothy Rogers in Stantonbury, where he stabbed the 48-year-old woman 31 times. Her 19-year-old son, Michael Rogers, was chased to a nearby playground, where Davis bludgeoned and disemboweled him. Another individual, Mick Cowles, was attacked with a hammer and seriously wounded.

Davis was arrested the same day. At his trial on December 15, 2003, he pleaded guilty to manslaughter on the grounds of diminished responsibility. A team of five psychiatrists diagnosed him with major depressive disorder, social anxiety disorder, alcohol dependence, and a psychotic episode at the time of the crimes. He was sentenced to an indefinite term at Broadmoor Hospital.

In 2009, Davis was transferred to Littlemore Hospital, where he was allowed short releases. A Mental Health Review Tribunal approved his release in July 2011.