A former missionary convicted of committing sex crimes against children while at an African orphanage is set to be sentenced Monday morning by an Oklahoma City federal judge.

The sentencing ultimately will determine the likelihood of Matthew Lane Durham ever going free.

U.S. District Judge David Russell must decide the punishment on Durham's four counts of engaging in illicit sexual conduct in foreign places. The four counts involve three girls and a boy ranging in age from 5 to 14.

Prosecutors last month asked the judge to order Durham, 21, of Edmond, to serve the maximum punishment for the four offenses — 30 years for each count, running consecutively, for a total of 120 years in prison. Durham's defense attorneys plan to ask for an eight-year prison sentence plus probation since he has no criminal history.