MACON, Ga. (AP) — Investigators have revealed at a court hearing what led them to charge a law school graduate with the killing and dismemberment of his classmate.

Macon police detective David Patterson testified on Friday that police found a bloody hacksaw linked to Stephen McDaniel as well as master keys to an apartment where Lauren Giddings lived.

He also said McDaniel had outlined what he considered a "perfect murder" to a former roommate.

McDaniel is charged with murdering Giddings, who lived in an apartment complex across from Mercer University's law school.

The 25-year-old McDaniel has pleaded not guilty. His attorney has cast doubt on the thoroughness of the investigation and suggested others could have gained access to Giddings' apartment.

McDaniel and Giddings both graduated from Mercer's law school in May.

Giddings, a 27-year-old from Laurel, Md., was last seen June 25. Police discovered her torso five days later wrapped in plastic in a garbage bin near her Macon apartment building.

McDaniel has also since been charged with seven counts of sexual exploitation of children linked to inappropriate images authorities said they found in his apartment.