Q. Can criminals be counted in a minyan? Since they have publicly desecrated God’s commandments, wouldn’t counting them in a minyan defeat the notion of a “spiritual quorum” for prayer?
One transgression does not excuse another, and indeed praying in a minyan may well turn the person’s thoughts towards repentance; the sages often warn against “closing the door before penitents”.
A fascinating Australian episode which helps to clarify the issue derives from convict Tasmania about 150 years ago.
The president of the Hobart Hebrew Congregation wrote to Chief Rabbi Nathan Marcus Adler in London asking whether convicts could be called to the Torah.
It took months for the enquiry to reach London, and months for the answer to come back, but the Chief Rabbi ruled that convicts and “ticket-of-leave” men could attend services and be counted towards a minyan, but should not be called to the Torah or accorded any honours (Max Gordon, “Jews in Van Diemen’s Land”, 1965, p. 90).