Punishing the trio, the court relied on the testimony of Sapna, a ninth-grader and a cousin of the deceased who was present with him during the time of the murder.
Additional Sessions Judge Sanjay Garg sentenced East Delhi residents Mohd Imran (20), Akram (20) and Mukesh (21) to life imprisonment for murdering Dhiraj and seven to ten years in jail for robbing him of his money and mobile phone.
"Statement of prosecution witness (Sapna) is consistent, credible and trustworthy. I find no reason to disbelieve her testimony," the court said.
"In view of aforesaid discussions, it stands established beyond doubt that all the three accused sharing common intention voluntarily caused hurt to deceased Dhiraj while committing robbery," the court added.
Narrating the sequence of events, Sapna told the court that while on her way to her friend`s house on April 18, 2010, she met Dhiraj and asked for his science book.
While talking about the books, they went to Sanjay Jheel Park for a stroll and sat there at a bench, she said, adding that at about 11 am, three youths turned up there and enquired Dhiraj about the time.
As Dhiraj took out his cell phone to check the time, the trio asked him to hand over the phone and when the boy refused, Akram and Mohd Imran caught hold of him and Mukesh stabbed him in his chest.
After assaulting Dhiraj, the trio snatched his cell phone, searched his pocket and took out Rs 70 along with an ATM card and fled away leaving him bleeding profusely, Sapna said, adding that after she raised an alarm the boy was rushed to hospital where he was declared brought dead.
The police later told court that it arrested the trio after putting Dhiraj`s mobile phone number on surveillance.
The number was found being used by Gulshan Bano, who turned out to be Imran`s mother, living in Jhuggi Jawahar Mohalla at Mayur Vihar in East Delhi.
During interrogation, Imran confessed to his involvement in Dhiraj`s murder, police said, adding that at his instance, Mukesh and Akram were also arrested and they both disclosed their role in the crime.