Grasses are common plant species encountered in botanical evidence because of their wide range of habitats. Presently forensic plant samples are discriminated based on morphological observation, however, some textures occasionally show similar characteristics among different species. In this study, discrimination of grass samples was carried out by comparison of rbcL partial region sequence, which is used as markers for phylogenetic and taxonomic studies. Sequence analyses were performed on 5 commercially available grass hay samples and plant fragments collected from 3 different cowsheds. The rbcL sequences of commercially available grass hay samples were characteristic to each other. All grass samples collected from the same cowshed had identical sequences, and the sequence was characteristic to each cowshed. Furthermore, different parts of the plant body could be analyzed and showed the identical sequences within the same sample. The results suggest that discrimination among grass hay samples was possible by comparison of rbcL sequences and DNA sequences used as phylogenetic and taxonomic markers will be useful for forensic discrimination of plant evidence.