Maybe.

It's fairly easy to get DNA sequence from mitochondria.

Um, even if it's kinda degraded, it depends on how degraded it is.

But the problem is, is that cousins might have identical mitochondrial DNA.

Siblings probably have identical mitochondrial DNA.

Mothers and children have identical mitochondrial DNA.

So you can't say, "I'm 99.99999% sure that this mitochondrial DNA came from this person," because it could have come from that person's sister or brother or cousin or whatever, mother, whatever.

Uh, even so, you could identify a suspect's family from that DNA, correct?