IIRC it is unlawful to jail conjoined twins if one commits a crime if the other twin was not involved. A loophole of American law.
How would the other not be involved?
For example, let’s say that conjoined twins that had two heads but one body. The left-side person was mostly dominant of the left side, and the right-side person was dominant of the right side. If the right-side person had texted a threat to someone, the left-side person could potentially be completely unaware and non-complicit in the matter. Now we can also imagine an infinite number of other scenarios that make it infinitely more complex, like for example, if one of the twins attempts but fails to kill the other, or more heinous crimes, like who was in control of the bowels when passing gas.