If someone has split personality and threatens that he or she will commit suicide, can it be considered as holding hostages?

No, I highly doubt it, because split personalities or not, it’s still only one person.

I doubt you’d have much success prosecuting for theft for using the other personalities car or money either.

No. Clever question, but no anyway,

From what little I know, the alternate personalities can come out to save themselves. But….what little I know.

In a movie, maybe …

Personality “C” isn’t threatening Personalites “A” and “B”, just themselves, so no.

But personalities A & B are aware that they share the same body as C. From what little I know.

LMAO! Well a big, fat, A+ for imagination. haha
If a person with MPD gets into an accident can they claim their defense as it being their alter egos fault? haha