Lets get something straight. This whole going to a person's criminal record to justify a shooting is complete and utter bullshit.
Having a criminal record doesn't matter.
I'd argue that it matters to a degree after the fact, if not much other evidence is around. For instance, if you've got a predicate violent felon on his 2nd strike, who might be going in for his 3rd, it is certainly plausible that he could have a different mind set when dealing with police than, say, a misdemeanor drug offender, etc.... And it is certainly a reasonable thing to look at in sex crimes, etc....
As with most things, lots of grey area.