Only a head of government can lie in state. There is also lie in repose.
All pretty much means the same stuff.
I kind of like, “laid out in the parlor.”
When I was a kid, back in the Stone Age, here Down South, people were laid out in the casket in the living room while visitors brought tons of food...................
It's the place that makes the difference, not the position. To lie in state is a government honor and is a public viewing that takes place in a government building, usually a prominent one. To lie in repose is a public viewing in non-governmental building.