These are my interpretations - someone who knows better may come along shortly!

The jury were out for an hour and a quarter; that's not very long for the jury to reach a guilty verdict. The prosecution's case must have been very convincing.

all stitched up by a Thin Blue Line; literally, to stitch up is to sew with a needle and thread. But to stitch someone up means to blame them for the acts of someone else. False evidence would come from the police - Thin Blue Line. Here, the Thin Blue Line can also represent the thread.

a slip of the finger, a sleight of hand; these, I imagine, are the   alterations to the hand-written notes made by the police, and the deceptions in the false confessions presented in court as evidence.

Another try at the Quarter Sessions; perhaps this means another attempt to gain a wrong conviction.