A police informer linked to the murder of human rights lawyer Willie Kimani and two others smoked at least five cigarettes at the suspected killing field.
Cigarette butts recovered from a deserted open field where Kimani, his client Josephat Mwenda, and taxi driver Joseph Muiruri are said to have been mercilessly killed, matches the informer's DNA profile.
Peter Ngugi Kamau, according to the DPP, had confessed to participating in the gruesome plot to eliminate the lawyer's client.
The suspect later denied.
An expert from the government chemist on Tuesday told the trial court that the cigarette butts could not have come from anyone else but Ngugi.
Dr Joseph Kagunda Kimani said filters in the cigarette butts retain DNA profiles better and it was easy to match them with that of the accused person.
"The probability indicates that it is not possible to find a similar match in the current existing population."
"The only DNA profile that can get close to matching can only be found from an identical twin," the expert said.
Soiled underwears, dirty trousers, vests, trousers they wore on the fateful night were also brought to court.
Samples of faeces, water bottles, and juice cans were part of the 170 pieces of evidence the court is looking at in a bid to unravel the murder.
Also produced were wooden bars, electricity cables, gunny bags that were used by the killers of the three who were found dumped in Ol Donyo Sabuk on July 1.
At the beginning of the high-profile murder case, the prosecution told the court that Ngugi- a standard eight drop out, confessed to have participated in the scheme to eliminate Kimani's client.
The scheme was allegedly orchestrated by Snr Sergeant Fredrick ole Leliman who is facing trial alongside Stephen Chebulet, Silvia Wanjiku, and Leonard Maina Mwangi.
Investigators believe the plan was hatched on June 22, 2016, at a hotel in Mlolongo.
On June 23, it is believed Kimani, Mwenda and Muiruri were arrested after a hearing a case involving Leliman at Mavoko law court.
They were held briefly at the Syokimau police post and later dragged to the open field at Soweto near Mastermind Tobacco where they were killed.
Earlier, Kizi Shako, a police pathologist who assessed the AP officers and the informer before they were charged denied that Ngugi was in distress.
"He was in fair general condition, composed and his memory was intact. He did not cry," the doctor said.
Although Dr Kagunda said there was no direct DNA match to the other suspects, he explained that it would be difficult to distinguish once they are contaminated.
The hearing resumes today.