Gateri was roughed up by CID officers at a Nairobi hotel where he was in a meeting with his lawyer Goergiadis Majimbo.
Not yet clear where Gateri has been taken to.
Samuel Gateri, the witness who filed an application to withdraw from Dennis Itumbi's case, has been arrested.
Gateri was nabbed by DCI officers at a Nairobi hotel where he was in a meeting with his lawyer Goergiadis Majimbo and taken to Shauri Moyo police station.
According to the lawyer, the officers arrived at the hotel in two cars, did not introduce themselves nor state the reason why they arrested Gateri.
"I tried to intervene to establish why he was being arrested, but the officers, and we don't know whether they are really officers or not, were violent, bundled him in a car and sped off," Majimbo said on the phone.
This comes a week after the office of the Director of Criminal Investigations dismissed claims that Gateri was among the state witnesses lined up to testify in Itumbi's case.
Through its Twitter handle last week, the DCI said Gateri is a man under investigation and at no point was he lined up as a state witness.
However, Gateri's name was among the names listed by the prosecution in the charge sheet against Itumbi.
Gateri had previously told the court that police officers had forced him to admit he had talked to Deputy President William Ruto in Itumbi's La Mada Hotel assassination plot case.
Gateri had admitted in court papers that he was a member of the Tangatanga WhatsApp group that the police suspected was behind a letter that was widely circulated, in which there were claims a group of Cabinet Secretaries held meetings at La Mada Hotel and planned how to eliminate Ruto.
Initially, he was to be a prosecution witness but has now changed his mind.
He asked the chief magistrate's court to enjoin him as an interested party and his statement to be produced in court claiming that he was forced to sign it.
Gateri also claimed his life is in danger citing threats and attempted kidnap.