DS Luke Stone's mobile phone uses the theme from the '70s classic British cop show The The Sweeney (1975) for its ringtone.
S2:E3 - The car in the hit-and-run clearly has a smashed windscreen, but when it's found, it is undamaged.
S2:E4 - One of the leading clues at the beginning is the towel with burn marks used as a silencer for the gun. However, at the end when the murder is reconstructed, no towel is used.