Quora Answer: If a Conjoined Twin Commits a Crime, How Do We Determine Which One Actually Did It?

The following is my answer to a Quora question: “If a conjoined twin commits a crime, how do we determine which one actually did it?”

Firstly, we have to know where they are conjoined.  This helps us understand how to go about determining plausible guilt, and opportunity to commit the crime.  Also, some conjoined twins involve one parasitic twin, meaning that there is only one legal person in this case.

Secondly, conjoined twins are always identical, monozygotic, where there is an incomplete separation during cell division.  What this means is that the DNA will be almost identical, and that goes to blood type, and other body fluids.  However, fingerprints, toe prints, tongue prints, and even dental records are distinct.  They can be told apart legally, if there is such physical evidence.

We must also remember that the use of the hand causes distinct angles of impact, and it may be possible to narrow down which hand was used, for example, in a stabbing incident, or in shooting a gun.  It is the same with the leg, and footprints.

Finally, as part of the investigative process, there is the police interview.  The challenge here is that both twins cannot be interviewed separately.  Thus, it will take skill to match their body language with the account, and pinpoint the approach.

Coming back to the first point, since both twins are always present at the commission of the offence, one or the other is the perpetrator and accessory.  However, if it is a capital offence, unless both are guilty, we cannot sentence the other to death since the law precludes the death sentence on the twin who is not guilty of the capital charge.