I read a lot about this case a few years ago - the more you read about it, the more puzzling it gets. In fact, if you let it, it'll drive you nuts.
For what it's worth, I am fairly sure that Wallace did it, but if he did, then why? Was it just simply that he didn't get on with his missus? If that really was the motive, then there'd be a queue a mile long of fed-up husbands waiting to be tried for murder. Did he set Parry up? If so, then he probably felt he had a legitimate reason to do so, as Parry was a wrong 'un and Wallace suspected him of stealing money from his house. I used to think that the main reason Wallace was reprieved was that his version of the timing of his activities that evening was eventually accepted; now, I'm not so sure.
The other thing is, How about the garage mechanic John Parkes who was cleaning Parry's car and discovered a pair of blood-stained gloves in the glove-box? I understand that Parkes claimed right into old age that his story about the glove was true, but I'm still not sure why it was apparently never used in a potential case against Parry? Oh well.....
We are suffering from a plethora of surmise, conjecture and hypothesis. - Sherlock Holmes, The Adventure Of Silver Blaze