Which of the following is used to detect old blood stain in a murder scene?

Precipitin Test and Latex test are used to differentiate whether human blood or animal blood. Benzidine test is used to detect old blood stains. A combination of two immunologic tests, mixed agglutination and immunofluorescence, that permits the detection of two AB0 system antigens in the same cell within one process. Such mode better validates the conclusion on the group appuenance of cells in analyses of mixed stains originating from different subjects with different blood groups.