Police have recovered the knife allegedly used by 20-year-old Sahil to kill a teenage girl in northwest Delhi's Shahbad Dairy area, police said on Thursday.
A senior police officer said the accused's police custody was extended for three more days by the court on Thursday.
He was again questioned and on his instance, the weapon of offence was recovered, the officer added.
Sahil was cross-questioned as he frequently changed his statements, he said, adding the three friends of the victim, Bhawna, Ajay alias Jhabru and Neetu, too were individually questioned and their versions corroborated.
The officer said the route taken by the accused while fleeing the crime scene has been established.
On Wednesday, police had recreated the crime scene.
Sakshi (16) was stabbed over 20 times and bludgeoned to death with a cement slab allegedly by Sahil on May 28. She had 34 injury marks on her body and her skull was raptured.
Sahil was arrested from Bulandshahar in Uttar Pradesh the next day.
He had allegedly thrown away the knife after the crime into the bushes at Rithala.
Police had said during interrogation, Sahil told them that he was angry after Sakshi rebuffed him in front of her friends and refused to get back to him.
The two were in a relationship that had turned sour, according to the police.
The probe carried out so far has revealed that no one was involved with Sahil in the crime, police had said, adding the accused confessed to have executed it himself.