Review: Witnesses (S1 E5&6/8), Saturday 9th December, BBC Four

NB: SPOILERS INSIDE After last week’s third and fourth episode – where Sandra Winkler and Catherine Keemer went rogue and formed their own crime drama version of Thelma and Louise – things are now bubbling nicely on Witnesses, although Sandra’s torturing of suspect Martin Souriau left a bitter taste in the mouth. You got the sense that…