[3mb3ry]

I think there's another thing to factor in for an inno/det killing the person that killed the rdmer and that is voice chat can get quite chaotic and clear communication is not always possible. There are countless times where I'm sure many of us cannot understand what's being said for numerous reasons, whether its too much side convo, you were focusing on something else happening in game, someone speaking to you irl, or whatever. So you could have easily missed the explanation in vc when you get dna.
Also, innos call detectives to bodies all the time and i believe most detectives only really check to make sure it is not a t body (and even then sometimes they dont check and kill someone for killing a T because they didn't check) before heading off to make the kill. I don't see many take the time to check every connection in the kill list before doing so.

Anyways, I bring this up only to mention that generally there is a lot more to this scenario when it does happen than just simply "I don't believe you *bam*"