Human rights lawyer Haron Ndubi was on Sunday night arrested in Nairobi, with police claiming he was driving drunk.
Activists have, however, claimed that he was arrested and drugged and is currently being held in critical condition.
Nairobi Police Commander Japheth Koome disclosed that they picked up Ndubi at around 8:45 pm on Jakaya Kikwete Road.
They claimed that he had already parked his car in the middle of the road and was sleeping in it.
Koome stated that the lawyer would on Monday morning be charged with driving under the influence of alcohol.
Activists led by Alamin Kimathi have, however, refused to buy the police story and insist that the suspect was drugged.
On Sunday night, Kimathi tweeted that Ndubi was 'in critical condition at Kileleshwa Police Station'.
He further alleged that the lawyer had been drugged near State House and police arrested him 'instead of taking him to the hospital.
Ndubi was part of the legal team that challenged President Uhuru Kenyatta's victory in the repeat Presidential election of 2017.
He represented activists Njonjo Mue and Khelef Khalifa who eventually lost the case as the Supreme Court upheld Uhuru's win.