Hi. Couple of things:
It is still only smaller companies which take the manslaughter hits - not saying it's right, just saying. So the case studies up to now aren't always that helpful.
Do you have risks assessed as being of serious consequence? Are these given top priority?
Also if you have have or can develop a method of capturing and then rating (as serious) incidents, close calls etc. however trivial, this will both justify your concern and create a basis for your presentations. Otherwise you are all just sitting waiting for the biggy.
So you are trying to get across how realistic is it really that something major WILL happen, and then if it does, will snr management be vulnerable? Beyond the company. In theory the answer is yes of course, but in reality, unless failings are 'gross', the enforcers will tend to take the easiest option.
Finding some cases in your particular industry could help (rather than something completely alien), but it is an unlikley event for MDs to be taken to the wire.
You could try going down the 'I want to prepare a crisis plan' route; where you can cover "what we will do if ever . . . ".
That gives you the opportunity to explain, almost as a story, what actually would happen - the police turn up, area is a crime scene, witnesses are 'to a crime' potentially, work / production comes to a halt, everyone, including senior managers, will be doing nothing else but managing this crisis, then HSE turn up, hand over any and all unpriveledged documents & other evidence - you get the picture.
Ask how legal support will be provided - to individuals, (including MD) not just the company. By whom. Cover the length of time to coroner inquest, prosecutions, and finally civil claims. Traumatic incident / employee support provision. Etc.
Don't make it too personal, or suggest any of this WILL happen, treat it almost as a business continuity matter, but this may drip-feed information which may ultimately motivate. If it doesn't, at least you will have a plan anyway.