Refers to a person serving a sentence in a correctional facility. More formal and specific than 囚人 (しゅうじん), which can also mean 'captive'.
About 500 prisoners are housed in that prison.
Programs that support the reintegration of convicts into society are important.
受刑者 is a general term for any inmate serving a sentence, while 死刑囚 refers specifically to someone sentenced to death.
Compound of 受刑 (じゅけい, 'undergoing punishment') + 者 (しゃ, 'person'). The term is a straightforward Sino-Japanese construction.