The Home Secretary has explained this apparent anomaly insofar as the death penalty has long been abolished in the UK. "Our longstanding opposition to the death penalty has not changed. Any evidence shared with the US in this case must be for the express purpose of progressing a federal prosecution."
From time to time polls have indicated that there are deep divisions in this country on whether or not Parliament should reverse the abolition decision which was initiated half a century ago and when assurances were made by parliamentarians that adequate custodial sentences would not lead to increases in homicides. This was a fatuous affirmation to the great British public. Proponents of the current position are quick to cite that only a few nations including certain states in the USA use the death penalty and that these are indeed mainly countries where democracy is in name only.
Two years ago a poll indicated that EU Leavers were sympathetic to bringing back capital punishment. Last year Sky News published a poll showing that Conservatives had a majority also similarly in favour. Having the good fortune to still be on this Earth after having enjoyed three scores year and ten and having been accused of being a dinosaur I am firmly of the belief that social mores work on a cyclical basis where opinions swing just as the weight of a pendulum reaches its amplitude and reverses its direction of motion. I believe that we are in just such a situation where the amplitude is about a decade or so from the vertical. The discussions over the EU are just a single example of this. The return of capital punishment could be another.