Being buried alive may be accidental or intentional.
Accidental:
(1) occupational (miner, trench collapse)
(2) environmental collapse (avalanche, etc)
(3) war-related
(4) iatrogenic (coma)
Intentional:
(1) buried after attempted murder
(2) punishment (Vestal virgins, cask of amontillado)
If there is an airspace around the person then the person dies of asphyxiation. If the person is completely buried the person may not be able to respire.
Evidence used to determine that a person was buried alive:
(1) a vital reaction (dust in airways)
(2) circumstances together absence of another explanation
Differential diagnosis:
(1) being killed during a rescue attempt
(2) ground movement from postmortem changes with gas formation and bloating
Some people develop a phobia about being buried alive.