Thanks, it seems similar in that case to the issue as regards 'dangerous cycling' in that thread. It's about the process. It's obvious though that this is a bigger priority given the numbers.
Although superficially they might seem similar, to my mind there are some major differences.
Firstly, as you point out, numbers. Incidents involving deaths due to cycling are tiny. By contrast the statistics on alleged incidents of spiking are huge - nearly 7000 last year. And I suspect this is the tip of an iceberg as I'd imagine many incidents go unreported. I think we can be pretty confident that a death on our roads or pavements involving a cyclist is not going to be unreported so the statistics will be an accurate record of the actual level of incidents.
Secondly - spiking involving prescription or illegal drugs is relatively new phenomenon, which is very much on the increase. Deaths involving cyclists are nothing new - they have been happening since bikes were around and the evidence suggests they are probably on the decline, albeit numbers are so small trends are hard to detect.
Third - intent. I doubt anyone who ultimately causes death on a bike goes out with the intention to kill, or to commit a crime. They may well be reckless or dangerous and should have foreseen potential consequences, but that it different to intending what actually happened. By contrast someone who spikes a drink, clearly intends to do this, so intends to commit a crime.
So on the third point I can see how a specific law on spiking, with the publicity that will ensue, may act as a deterrent (as was as to ensure convictions) as those intending to commit a crime may have second thoughts if it is absolutely clear that their intention is criminal. I don't see the same deterrent in the case of cyclists as they don't intend to commit a crime and likely won't think this would happen to them as they get on their bike.
And the final, and most important point - I cannot see why changing the law on cycling will make any material difference to the rates of charge and conviction (perhaps on sentencing, but that is a separate manner), simply because there is no evidence that dangerous cyclists are killing people and 'getting away with it'. That seems to be hugely different to spiking where it seems evidently clear that loads of people are spiking drinks and 'getting away with it'.