Kanja brings nearly four decades of law enforcement experience to his new role.
They say abductions and extrajudicial killings continue with impunity despite the president's promise to end the practice.
Gaitho was arrested outside the Karen police station in the company of his son who filmed the arrest raising alarm across the media fraternity.
Thus far, Director of Public Prosecutions (DPP) Renson Ingonga has directed the police to investigate the discovery and submit its findings within 21 days.
His admission that police abductions were happening came days after he defended the police against claims that they kidnapped former Nandi Hills MP Alfred Keter.
The party criticised President Ruto for distancing his administration from the killings and abductions despite what it said was clear evidence to the contrary.