Now, I don't say that he was definitely guilty of misconduct, or even probably guilty. But the salient issue, as I see it, is whether PC Mizen considered that there was a real risk that he could be subject to a misconduct inquiry. If so, he had a motive to lie.
The only motive to lie would be if he had been told of a criminal case or an accident.
He wasn't told of either of these things, on any view of the evidence, therefore no motive to lie.
And further there wasn't a single suggestion in 1888 that he could be in any form of trouble for not taking the carmens' particulars. He wasn't even asked at the inquest. It's a wholly modern criticism.
This is from a Judge of that period. "Complete,in the sense of being entirely exhaustive, the manual cannot and does not pretend to be"
The duties of the police,are for the most part,defined by statute.