I think I had better change the answer in my post, or rather add to it.

Is crime passionel a sign of love, or of love dead?
Mindless stupidity.

Not all is the above because some are carried out with a lot of forethought.

What causes crime passionel?
In most cases it could be a possessive and jealous person; cheating, verbal assault, drink, or a combination of any.

What if a person helps their spouse to commit medical suicide because they are terminally ill? By either giving them the drugs to do so, or taking them abroad. If they never helped them with this euthanasia the person would die a painful and degrading death in a month, year. Is that really euthanasia, suicide, murder or a crime of passion?

Be well IAN 2411