Using the indefinite article a with the word final has always confused me. I mean how come something that is final can be considered indefinite! When it's final, it's definitely final, isn't it?
An investigation report from Marin County Sheriff’s Office Coroner Division confused me further. It reads...
At this time, the Sheriff’s Office Coroner Division suspects the death to be a suicide due to asphyxia, but a comprehensive investigation must be completed before a final determination is made.
When we investigate something and come up with our final decision, it's pretty final. Something like...
"After evaluating our company's situation today, we have come up with the final decision of shutting it down."
About Robin William's case, when those investigators will look into the matter and come up with something authentic, that's the final decision/determination. After all, it's legally declared. They must come up with the final decision because there cannot be two final decisions or final decision that's random! Using a final decision triggers some funny examples in my mind - a final decision, thereafter another final decision and then a random final decision and after those many final decisions, the final decision! :)
In fact, in that particular sentence (after reading examples of COCA for 'a final' sentences), it should have 'the' because they are telling something (investigation) must be completed BEFORE a final determination is made. They are pretty concerned about the determination and hence want to go for a comprehensive investigation. After doing that hard work, they don't come up with a possible final statement. When it's final, it's not something possible. Again, there cannot be two finals or a random final to support a final statement and not the final statement.
I look this quite similar to using a with result. When the result is out, the result is out and not a result.