Definite human patient NPs are marked. Indefinite human patient NPs are optionally marked depending on whether the referent is specific or not, yet also depending on the degree of recognition that the speaker grants the patient NP. Non-human animate patients are not normally marked, unless highly definite. Inanimate patients are not marked.
Source: Baxter 1988: 156
Source: Baxter 1988: 154
Source: Baxter 1988: 157
Source: Baxter 1988: 159