Jurors have been warned against the urge to “play detective” in the real life “whodunit” of a mother and her lover accused of murdering eight-year-old Ayesha Ali.

Polly Chowdhury, 35, and Kiki Muddar, 43, are on trial at the Old Bailey over the death of the little girl at their home in Chadwell Heath in August 2013.

The court has heard how Ms Muddar seduced Ms Chowdhury through a cast of fictional characters on Facebook and via text messages which she used to turned her against Ayesha because she saw her as a threat.

Ms Muddar denies being at home at the time the child received a fatal head injury, despite Ms Chowdhury claiming she was giving her a cold bath as punishment for wetting herself around the time she was hurt.

In his closing speech, Ms Muddar’s lawyer Henry Blaxland QC said the case was “challenging” because nobody could say exactly how Ayesha died and it was human nature to try to solve the CSI-style puzzle.

He said: “This case is a huge challenge because when it comes down to it, this case is a whodunit. Was it both of them or one of them, and if so which one?

“It’s a human instinct to want to solve problems. There’s a huge industry which is based on that human instinct. You can barely turn on the TV without watching a whodunit drama.

“CSI is based on our instinctive urge to solve mysteries and there’s nothing more frustrating than not being able to solve a crossword puzzle, but the truth is no one knows exactly how Ayesha died.”

He said there may be an urge to “play detective” and scan through the defendants’ text messages for clues, but he said: “It is of the greatest importance not to allow your imagination to get the better of you to solve the puzzle.”

Mr Blaxland also told the jury: “It is difficult you may think hearing the evidence in this case not to be overwhelmed by sympathy for Ayesha Ali, not to be overwhelmed by a feeling of abhorrence of what happened to her and the desire for those responsible for her suffering and death to be punished.”

Mr Blaxland said they must consider the case in an “analytical and dispassionate” way.

“When considering the case against Kiki Muddar the question is not was she responsible for the death of Ayesha Ali but is she in law guilty of the grave crimes against her,” he said.

Ms Muddar, of Green Lane, Ilford, and Ms Chowdhury, of Broomfield Road, Chadwell Heath, deny murder, manslaughter and causing or allowing the death of a child.