The four-hour ordeal was captured in a confession made by Mr Ngugi, who had been hired by Mr Leliman to help him carry out the job.
The main target was Mr Mwenda, who had filed a complaint against the officer. He was to be captured and killed after the court hearing.
A video recording explaining how lawyer Willie Kimani, his client Josephat Mwenda and taxi driver Joseph Muiruri were executed is expected to be played in the High Court Wednesday morning.
The recording was made by Joseph Muindi, a senior officer who was tasked with capturing former police informer Peter Ngugi as he took a detective to the spots where the three were killed on the night of June 23, 2016.
On Tuesday, Mr Ngugi, through his lawyer Kevin Michuki, raised an objection, saying the court should not allow him to incriminate himself.
Justice Jessie Lesiit adjourned the matter to this morning.
Mr Muindi told the court that he was approached by detective Clement Mwangi asking him to accompany him as the accused person took him to the crimes scenes.
Mr Muindi said he cautioned him, read the charge sheet to him and told him of his rights. He said Mr Ngugi agreed to go ahead and be recorded. They visited six crime spots, where the recording was done as Mr Ngugi explained how it happened.
The first spot they visited was the Mavoko Law Courts, where Mr Ngugi kept watch as Mr Kimani and his client Mwenda attended a hearing over an assault case that the latter had filed against Mr Fredrick Leliman, one of the accused.
They later drove a few kilometres in Athi River and were shown where Mr Muiruri was stopped as he drove towards the city centre after the hearing was concluded.
Mr Muindi told Justice Lesiit that they then drove to Limuru and were shown where Mr Ngugi abandoned the taxi belonging to Mr Muiruri before they drove back to the Syokimau AP camp, where the three victims were held for several hours.