Just thinking that the 'always' search for anything administrative, paperwork, license, etc is important but not looking for the cause of an accident.
The cause here, from the report, would appear to be CO poisoning and/or loss of control and /or pilot inexperience and/or weather..
I always feel that the actual lack of a certificate is not a cause. A pilot may have experience but no certificate or he may have a certificate gained only three or four hours flight time before. It is the lack of experience rather than the paperwork, surely, that is the hole in the cheese.
A couple of times I have been to airshows where pilots boasting that they got their PPL a couple of months before have been giving charity rides to people, even kids. My personal thought is "Are you stark raving mad?" Yes, technically the certificate says you can fly passengers (Non paying) around but other peoples' kids?
Sorry, thread drift for hobby horse.