Gill said phone data puts him at the canyon a week after Lueck disappeared. Police obtained a search warrant for his home the next day.
Ajayi was arrested June 28 during the wide-ranging search for the 23-year-old University of Utah student that lasted nearly two weeks. Prosecutors did not strike a deal with Ajayi to find her, Gill said.
Ajayi was charged with one count each of aggravated murder, aggravated kidnapping, obstruction of justice and desecration of a human body. A court appearance was set for Monday.
Ajayi is represented by the public defender’s office, which has refused to comment on the case.
The charges make Ajayi eligible for the death penalty, but Gill did not say whether prosecutors would pursue it.
Lueck has been remembered as a bubbly, nurturing person. She was a member of a sorority and a part-time senior at the university studying kinesiology and pre-nursing.
Ajayi is an information technology worker who had stints with high-profile companies and was briefly in the Army National Guard.
He has no formal criminal history but was investigated in a 2014 rape allegation and was arrested in a stolen iPad case at Utah State University in 2012. The arrest and the expiration of his student visa led to him being banned from the campus for about three years.
A native of Nigeria, Ajayi holds a green card that allows him to legally work and live in the U.S., Gill said.