It is not clear how and why the two women decided to go to Ms Mungai’s residence, and this will be a key factor in establishing whether the murder was premeditated.
According Mr Mathenge’s account, the women started arguing over Mr Kori’s photos in the house and the logbook of an identical Mercedes Benz, which Mr Karue had apparently bought for the mistress.
A fight ensued, Mr Mathenge said, and the two wrestled over a knife, which Ms Mungai wanted to use to stab her rival, before the suspect rushed to the kitchen, grabbed a pressure cooker and hit Ms Wambui with it on the head.
The knife is part of the items that police found at Ms Wangui’s residence and forwarded for forensic examination.
The pressure cooker has not been found after it was thrown in a thicket along the Ruiru-Kiambu road.
Mr Mathenge said when Ms Wambui screamed for help, Ms Mungai suffocated her to death, dragged the body to the kitchen, and wrapped it in bedding.
A post-mortem report seen by the Nation shows that she was hit with a blunt object nine times and suffered internal bleeding to the brain.
Mr Mathenge said Ms Mungai called him around 10pm from Homeland Inn, where she was trying to get another car she had hired to dispose of the body.
Security guards refused to let her take the vehicle because she had no gate pass.
She drove back home in Ms Wambui’s car. Mr Mathenge arrived several minutes after midnight in his Toyota Noah. They left again for Homeland Inn in his car but could not convince the guards to release the other vehicle. These movements were captured on CCTV.
They drove back to the estate, parked Mr Wambui’s car near the stairs, carried the body downstairs, and placed it in the back seat. The two then used the Kiambu-Kamiti-Ruiru road, escaped a near-detection at a roadblock at the Kamiti Junction and proceeded to dump the body at Mugutha.
While on their way back, Mr Mathenge said they stopped at Gitambaya, between Ruiru and Kiambu, where Ms Mungai threw away the pressure cooker and the bedding.
These have been taken by police as well as keys believed to be for Ms Wambui’s house, a baby car seat that had been displaced from the back seat to accommodate the body, and a black polythene bag in which the pressure cooker was wrapped.
Detectives suspect that the cooker and the carpet, which are missing, may have been later retrieved by a passer-by either for sale or for use.
Ms Wangui and Mr Mathenge then proceeded towards Githunguri through the Kirigiti-Riabai road, where they threw away a blood-stained carpet.
They abandoned Ms Wambui’s car at Kwa-Maiko trading centre, where it was recovered two days later. They arrived back in the estate at 5am in Mr Mathenge’s car.
Police have impounded five vehicles, including the two Mercedez Benz saloons, Mr Karue’s Lexus SUV, a Toyota Allion and Mr Mathenge’s Noah.