Hey, I've seen emergency tracheotomy performed numerous times on telly, in movies, etc.... If I didn't know any differently, I could legitimately use that excuse for treating someone in that way if their life was in danger...
Same with applying butter to burns. If You've always been told that appying butter to burns is an acceptable form of treatment (and I'm sure many of you have too - some of you may still believe it!) If you've never attended a first aid course to be told differently (and someone on my last course genuinely believed that butter should be in a first aid kit), then nobody can complain if you then apply butter to burns! (using a basting brush?)
They genuinely believe they were doing the right thing, they've seen it being used elsewhere and have never been told any differently.
Arguably, they are unlikely to be successfully sued, but I'd suggest they'll then have to live with the outcome of their actions.
As good a reason as any for everyone to do some kind of first aid trianing.
Frankly, if someone is being strongly cross examined for performing CPR because their ticket is 6 months out of date, then the "persecution" should be taken out and shot. They did the right thing, period.