A judge today indicted Milani in the case of Alberto Ledo, who was a 20-year-old university student assigned as an aide to Milani during his mandatory military service.
Prosecutors say Ledo vanished after a captain summoned him one night, and Milani helped present the case as a desertion.
The motive is not clear, though the military was carrying out a murderous purge of suspected leftists at the time.
Milani headed the military under President Cristina Fernandez until 2015. He also is under arrest for alleged participation in the kidnapping and torture of three people during the dictatorship, which ended in 1983.