Black is charged with aggravated murder, child kidnapping and rape of a child in the Sierra Newbold case. He is also charged with molesting another girl several years before, and with robbing a bank. The preliminary hearing would have covered all three cases.
If he is ruled incompetent, Black will be hospitalized and further court dates will be canceled.
According to charging documents, Black allegedly abducted Sierra on June 26, 2012, from her West Jordan home about one block from his own home and beat, raped and strangled her before throwing her into a nearby canal, where she drowned.
Three days later, Black was arrested on suspicion of an unrelated bank robbery.
When he was taken into custody, investigators noticed soot and debris on his clothing and hands that was similar to the materials in a field where Sierra's clothes were found.
Lab results showed Black's DNA matched DNA found on Sierra's body, prosecutors said.
Last August, Black was charged with molesting the other girl from several years before. The girl, who would have been 11 or 12 years old at the time, attended a sleepover with members of Black's family sometime between 2007 and 2009.
Black, according to court documents, entered the bedroom where the girl was sleeping and touched her breasts, put his hands down her underwear and forced her hands to touch his genitals. The next summer, court documents say, Black lured the same girl to his apartment and again put his hands down her pants.
Black has sent letters to The Tribune from jail in which he has maintained his innocence. He said police were looking for someone to pin Sierra Newbold's murder on, and he got was an easy target, who got caught up in the investigation.