Mulakhil had “repeatedly insisted” the girl went with him voluntarily, adding he believed she looked like she was aged in her 20s.
But it would have been “obvious to anyone that she was a very young, vulnerable child,” said Oscroft.
The court heard Kabir is alleged to have strangled the girl, who had been playing in a park, at about 18:00 BST.
She was then seen talking to Mulakhil at about 20:00, when she is said to have claimed to be aged 19.
Oscroft told jurors the girl’s claim was “such an obvious lie” that it was clear from Mulakhil’s reaction that he did not believe her.
Mulakhil was also in contact with Kabir, the prosecution added, and their discussions appeared to be about their alleged victim.
The court heard she was “forced” to engage in sexual acts, and had disclosed on the same night as the attack that she had also been “smacked and pulled”.
Mulakhil’s phone was seized after his arrest, jurors were told, and indecent images and images of the two defendants together were found, confirming they were well known to each other.
Oscroft said investigators also found Mulakhil’s DNA on the girl’s neck and on the inside of her clothing.
Mulakhil, denies child abduction, two counts of rape, two counts of sexual assault and taking indecent photographs of a child.
Kabir, also of no fixed address, denies intentional strangulation, committing an offence with intent to commit a sexual offence and attempted abduction.
Additional reporting by PA Media