Intent to Kill: Part 1

A gang of four criminals have raided a warehouse and a night-watchman has been shot and seriously wounded. Two of the gang have been acquitted of attempted murder at an earlier trial. The third member of the gang is now on trial after finally being apprehended in Essex. The fourth gang member, the getaway driver, has turned Queens evidence in return for police protection and is now being used as a prosecution witness. Is his evidence reliable enough?