It’s caught on a security camera. Plus there’s DNA from a strand of hair that fell off near the time of the murder. It’s an incontravertable fact that one of the them committed the murder.
But there’s no way of proving which twin did it. And both deny it and blame the other.
They obviously can’t lock both of them up since one of them is innocent. Would the authorities eventually be forced to let them both go?
well i assume they could look for motive and other non-physical evidence
but this reminds me of that old conjoined twins riddle. im sure its been discussed here, but what would happen if one conjoined twin kills someone?
From a strand of hair? Perhaps not. From a blood sample? Perhaps, but it is not a standard test. You see, the genes in the immune system that comprise the active region of antibodies reassort independently at a much later stage than most viable monozygotic twins separate. Each would have their own antibodies, which could be distinguished.
Though there can be other small differences between identical twins, they are below the threshold of reliable testing today (due to a lack of research in the field) and may always be unreliable – you see, there may be some small degree of mosaicism (slight differences in genome between different regions of the same individual) in everyone. The intact cells in the base of one hair may have very slight differences in genome from those of another hair (e.g. leg vs. neck) because genetic replication isn’t perfect. Usually these differences don’t have any effect, but if a mutation lands in the wrong spot, you may end up with a tumor. (though it is more common that a even a mutation in a key gene will simply result in nonfunctional or nonviable daughter cells.
Legally, this isn’t a very tricky issue. It’s no different from any other case where you have two suspects, but can’t prove either one guilty (e.g. due to a lack of evidence) – which is not altogether uncommon. The fact that the suspects are closely related doesn’t change anything.
A strand of hair could be compared to those on the heads of the two individuals; hair contains variations in compounds laid down at the time of growth, so it contains a record of certain aspects of the person’s body chemistry over time; very likely to be different, even for identical twins.
Fingerprints aren’t identical in identical twins. (Though this might be thwarted if the thief wore gloves, or if they both had prosthetic arms.)
As for the conjoined twin murdering someone? Easy. Lobotomize the guilty one. (Probably wouldn’t fly, legally, though. Lousy congress.)
A guy at my martial arts club used to be a bicycle thief. Yes, he was a Very Bad Teen, but he has since reformed, he’s no longer naughty and feels like a schmuck. But when he was 15, some guy used to pay him and some other teens to steal very expensive bikes for parts – forget about a fancy lock, they could cut the bike in half.
Anyway, one day he got caught. But he had no ID on him and provided the police with his twin brother’s name. So his brother is the one who eventually ended up in court. Anyway, it was kind of messy, but charges against his brother were dismissed, (he had an ironclad alibi), and my then-asshat friend got away with it.
Note: All officials, judge, prosecutor, cops, parents, everyone with authority were pretty ticked off. It was also made clear that if either one of them ever tried a stupid stunt like that again in order to beat the system, there would be hell to pay!
However, in a capital crime, the standards would be, much, much, MUCH more rigorous.
NOTE:
An important part of my martial arts colleague’s case: For whatever reason (maybe because he was a minor, or something), he wasn’t “processed”. They didn’t take him downtown to be fingerprinted or anything. He was only handed over to his parents with some kind of “notice to appear” in court… bearing his brother’s name.