A British man accused of murdering his American wife and their nine-month old daughter spent the month before they died trawling websites for sexual encounters, a court was told yesterday.

Prosecutors allege that, trapped in debt and dissatisfied with his sex life, 29-year old Neil Entwistle lived a secret life online, where he accessed websites about sex and killing before shooting his family. He denies killing his wife, Rachel and their daughter Lilian Rose, at their home in Hopkinton, Massachusetts, on January 20 2006.

Yesterday, Detective Lawrence James told the Middlesex County superior court that in December 2005 Entwistle used his credit card to pay for a month"s membership on AdultFriendFinder.com, a website describing itself as "the world"s largest sex and swinger personals community". He also visited a string of online escort agencies, James said.

Four days before the deaths, his username was also used for an internet search for the "best" way to kill someone, James said. He showed the jury a diagram recovered from Entwistle"s laptop which showed the major human arteries and a number of "strike points" in the chest. The diagram was downloaded after an internet search for "how to kill with a knife".

A person using Entwistle"s username also searched the internet for "knife in neck kill" shortly after 4.15pm on January 17. On the same day, the same user also searched for "quick suicide method".

Entwistle claims he had returned home to find his wife and daughter dead. He covered them up, and the next morning flew without luggage on a one-way ticket to the UK. He was later extradited back to the US. The trial continues.