Patient noun phrases are unmarked. Most transitive verbs have a transitivity marking suffix -im, but this is neither case-marking (because it occurs on the verb, not on the patient NP) nor head-marking, because it is invariable and therefore does not provide any information (e.g. person, number) about the patient.
Source: Sandefur 1979: 114
Source: Angelo et al. 1998
Source: Munro 2004: 142