Sounds dangerous approaching a large injured animal, with a knife 😕

Did they not show or recommend a suitable knife?

I would have said Cold Steel Outdoorsman. But you want a double edge blade. The Outdoorsman is study/thick but hollow ground so sharp as feck. IMHO for a blade of it's thickness is scary sharp after you get it on a waterstone of circa 3000 grit. It's not going to be as sharp as a Victorinox Fibrox utility/rabbit knife but those are like a damn scalpel. Just on thickness there has been a trend towards thicker knives born partially from what'll pass some youtube bullshit survival test. I've a knife that looks like an Old Hickory butchers knife I found in my Granny's lean to turf shed when I was a pup. Thin blade but I put it though hell as a kid. Don't be overly concerned about thickness unless yer batoning oak or something similar.

In reality how practical is catching an injured (but mobile) deer and severing an artery with a knife to finish it off?

Did you consider a 22lr pistol? There was a thread not too long ago discussing that very topic, and it seem a lot safer than a knife.

This is the one part of the HD course I was totally at odds with.

I've seen enough of them done in Germany,but it is VERY much a skill you would want to practise on a cadaver before you try this in real life.

As well as it being downright dangerous and leaving you liable to some serious injury.I know two professional old school German hunters who have got ligament damage in their hands after getting Roe deer antler prongs thru their palms while either trying to sever the spinal cord via the base of the skull and Atlas bone or trying a throat cut. A Roebuck isn't exactly huge,so consider trying this on a Red stag??? What was being said in the course of folding the deer's head into its neck to then cut the exposed neck was IMHO highly dangerous and irresponsible. It is now also illegal to do as a humane dispatch method in Germany anymore due to the animal rights mob and cruelty issues. It is now finish them off with a pistol or rifle and preferably away from public view.

That being said.No need to go all Commando with a double edge blade. The traditional German "Hirsh fanger" [deer catcher] blade used for humane dispatch is a single-edged 12/18in long bayonet like blade that has dispatched countless deer over the centuries. Google it for various pics and versions. So a bayonet in the style of an old French Lebel or the like would give you some stand off distance.

However, I would think a possibly better and more humane solution would be;

Silenced .22 pistol or CF if you still have. I'm sure if you could justify the need you could get an extension of use note from the relevant authorities for use outside a range and/or can?

3 to 4in Subcaliber insert for a pistol round in a shotgun. You are NOT hunting and you are not taking shots of any more than 10 feet. After all, you are supposed to be the expert dispatcher and have the situation under your control at the traffic accident scene. So you should be on top of the deer.

Seen a UK gunsmith /HD devise from an old single shot 410 "poachers shotgun" a great HD gun,by making an integral silencer and keeping it at a 25in length using a mesh screen and an old PCP rifle air tank as the outside tube. Very discrete and was hard to discen past 25 yards apparently in the sound As it can be folded up and hidden in a small bag or in a large coat pocket as you go about your job. Using wax or hilbilly slugs, if you cant get 410 slugs, would be a good option for a gun like this? They were even close enough to suggest using a shotgun with this kind of load on the course.

00Buckshot...That's what it was made for after all way back when.

In short, this animal has suffered enough already...You are not hunting you are doing a humane dispatch,so any other humane methods should be considered first off, IOW a firearm of some type,and then a blade...As a very last recourse,and you had better know what you are doing it and where. Hacking away at an animal on a public road where there has already been an accident and no doubt attracted rubberneckers,is not going to do us any favours or show professionalism to the AGS. I cant really see a justifiable reason or scenario where you need to put yourself at risk using this technique with even what we have here in guns available in Irl either.

Very nice looking knife!☺️