Neil Entwistle, now aged 40, was found guilty in 2008 of killing his 27-year-old wife Rachel and their daughter Lillian (pictured together left) in Hopkinton, near Boston, Massachusetts. But former IT consultant Entwistle (pictured top left during his murder trial) has written to Rachel's parents from prison to insist his wife (pictured together top right) had killed their baby (pictured with her mother bottom right) before turning the gun on herself. The letter is revealed in a book by Entwistle's 62-year-old father Cliff (pictured inset at his son's trial), who also maintains his son's innocence. The Nottingham engineer is serving life in prison in Massachusetts without the possibility of parole for their murders. Autopsy results showed that Rachel died of a gunshot wound to the head and Lillian of a gunshot wound to the torso. Prosecutors argued at the murder trial that Entwistle killed his wife and daughter because he was upset about his failure to find employment.