hapus capus, n. — Green’s Dictionary of Slang

hapus capus n.

also hapas capas

[a speedy, lazy pron. of Lat. habeas corpus, thou (shalt) have the body (in court). The prerogative writ habeas corpus ad subjiciendum, requiring the body of a person restrained of liberty to be brought before the judge or into court so that the lawfulness of the restraint may be investigated and determined. This writ is seen as the basis of all open, honest and democratic legal systems]

1. (US) habeas corpus.

1938		Signalman’s Journal 36: For a while I thought I would have to have Judge Magnuson serve a Hapus Capus or a Hokus Pokus, or something on him.
1956		Carpenter LXXVI 14: The Curbstone Lawyer: This is the frustrated attorney whose battle cry is: ‘It ain’t legal.’ He knows all about Hapus Capus and In Hoc Signo.

2. (US prison) a prison inmate who has made himself into a self-taught lawyer, to pursue his own case, combat prison corruption or help his fellow inmates.

1950

Goldin et al. DAUL 91/1: Hapas capas. [...] 2. An inmate amateur lawyer.