CHRISTIANSBURG, Va. — Nicole Lovell slipped out her bedroom window on a cold January night, seeking the promise of a romantic walk in the woods. The 13-year-old grabbed her cellphone and her “Minions” blanket, nurturing a dream of running away with the trim Virginia Tech athlete she had met online.

The secret rendezvous with freshman David Eisenhauer was a ruse, police testified Friday, part of an elaborate plan he hatched with a close friend to kill the middle-school student and keep his inappropriate relationship with her from becoming public. His friend Natalie Keepers also had a sinister motivation, a police detective testified, recounting how Keepers told police that she was a “sociopath-in-training” and that the secrecy and intrigue surrounding the murder plot gave her “the best feeling.”

Along a dark country road, in a swath of woods Eisenhauer and Keepers had scouted for the crime, police said, Eisenhauer stabbed the girl to death, blood staining the snow.

Detectives testified in a preliminary hearing Friday that the two Virginia Tech students believed they had planned a perfect crime. They shut off their cellphones; they hid the knife in the woods; they tossed Nicole’s belongings in a dumpster and a raging river; and they bathed her body with cleaning wipes before dumping it in North Carolina.

And they believed they would get away with it. Police said that Eisenhauer told Keepers that thousands of children go missing every year and are never found.

“It will never be traced,” Eisenhauer said in a text message to Keepers, according to police. “Always go overkill when your life is on the line.”

Detectives testified for three hours Friday, detailing how the pair plotted to end Nicole’s life and conceal the crime. Despite a conviction that the slaying wouldn’t be traced to them, police said, a series of missteps was their undoing: A GPS device in Eisenhauer’s Lexus remained on, tracking the car’s movements that night; Nicole’s blood seeped into the car’s trunk; and the two students later exchanged incriminating text messages.

Keepers, who broke down during an interview with police after Nicole disappeared, ultimately recounted to detectives how the crime unfolded and turned over her cellphone, police testified.

Eisenhauer, 19, of Columbia, Maryland, is charged with abduction and first-degree murder in Nicole’s death. Keepers, 19, of Laurel, Maryland, is charged with accessory before the fact and concealing the body. Mary Pettitt, commonwealth’s attorney in Montgomery County, Virginia, said Keepers helped Eisenhauer plan the killing and then helped try to cover it up.

A judge determined Friday that there is enough evidence to move the case against each student to a grand jury, which is scheduled to meet July 26.

The investigation began Jan. 27, when Nicole’s mother, Tammy Weeks, reported the 13-year-old missing after going to the girl’s bedroom and finding a nightstand shoved up against her door to prevent entry.