The commander and the clandestine unit: Inside OSU's expanding trail of allegations

Police commander Zachary Kariuki and OSU face scrutiny over allegations of abductions, torture and abuse of authority. [Courtesy, Standard]

Zachary Kiago Kariuki, the police commander at the centre of the Operations Support Unit (OSU), is facing renewed scrutiny over allegations of abductions, torture, and abuse of authority involving both civilians and officers under his command.

The scrutiny has intensified following the abduction and dumping of Standard Group Associate Editor Alex Kiprotich, an incident in which one of the officers captured in the operation has been identified as an OSU operative.

Kariuki’s rise has been marked by controversy. Records show that in 2013, he was a District Criminal Investigation Officer (DCIO) in Embu working under then-Inspector General David Kimaiyo. In 2023, he was controversially elevated to the rank of Commissioner of Police by former IG Japhet Koome.

Court documents now paint a disturbing picture of Kariuki's internal conduct, revealing a pattern of harassment against his own men. In a July 2025 judgment, the Employment and Labour Relations Court ruled in favour of Police Officer Benson Mang’ara Wangari, who sued the National Police Service over Kariuki’s conduct.

Mang’ara, who had served diligently for 10 years with a clean disciplinary record, claimed Kariuki subjected him to six months of punitive guard duties at the main entrance gate to humiliate him. The court heard that Kariuki openly expressed dislike for Mang’ara, threatening him with perpetual banishment to remote forward areas.

When Mang’ara was transferred to the Directorate of Criminal Investigations (DCI), Kariuki allegedly instigated his unlawful, repeated transfer back to the General Service Unit (GSU), in direct violation of Force Standing Orders and the National Police Service Commission Regulations.

“The repeated transfers caused immense psychological torture and disrupted my family life, forcing me to move my children from one school to another,” Mang’ara averred in his petition.

Justice Hellen Wasilwa found that Kariuki's actions violated Mang’ara’s constitutional rights to dignity, equality, and fair labour practices. The court quashed the irregular transfers, reinstated Mang’ara to the DCI, restrained the NPS from further harassing him, and awarded him Sh500,000 in damages for the infringement of his rights.

Beyond internal harassment, investigations by The Standard have pieced together a detailed operational matrix of the OSU, revealing a unit that operates like a parallel state. At the apex of this network is an influential top public servant based at State House. Beneath him lies an administrative ghost.

The unit’s footprint is deliberately elusive. It maintains "black site" offices unrecognised by official government registries—one along Valley Road, strategically positioned for telecommunications access, and another in Hurlingham. These are not locations that appear on any public directory or organogram; they are operational nodes designed to be invisible.

The fleet they use has a specific signature: in late 2022, ten vehicles donated by a former ambassador, bearing number plates between 120X and 129X, were assimilated into the unit.

The unit’s technological superiority is maintained from an operations centre at Teleposta Towers, a location chosen for its direct access to the "back door" of mobile network providers. From here, the unit can allegedly access real-time intelligence, bypassing standard legal protocols to track and target government critics.

Structurally, the unit operates as a regimented force of 45 operatives, divided into teams of seven, each allocated to a specific regional jurisdiction. The remuneration for this clandestine work is a sliding scale: operatives receive between Sh3,000 and Sh10,000 per "job," while their commanders pocket Sh15,000.

In another damning incident, several officers linked to OSU were allegedly involved in the abduction and robbery of a businessman in Hurlingham.

In February 2024, the Office of the Director of Public Prosecutions (DPP), after reviewing evidence in a harrowing case, saw Senior Assistant DPP Tabitha Ouya sign a damning letter naming seven OSU officers as culpable for torture. At the top of that list was Kariuki, who had been recalled from retirement to lead the very unit now implicated in some of the most egregious human rights violations in recent memory.

The advisory stemmed from the June 2023 arrest of businessman Abdulahi Abdille Isaack. According to the victim's statement, OSU officers arrested him at a Total petrol station in Hurlingham, Nairobi, where he had gone to buy medicine. What followed was days of unimaginable torture.

The victim was beaten, forced into a vehicle, and subjected to severe physical abuse that left him with injuries to his wrists, private parts, left leg, scalp, and eyes. Officers allegedly took his national ID and Sh1.94 million in cash. A Police Medical Examination report classified the degree of injury as grievous harm.

The DPP observed the torture was intended to force a confession to robbery with violence, a confession that never came because the victim had committed no crime.

The seven officers named in the DPP's decision are Kariuki, Corporal Ronald Chemosit, Chief Inspector Alexander Makoma, Sergeant Francis Singila, Constable Gabriel Kuria, Constable Jeremiah Chumba, and Constable Julius Lemayan.

Corporal Chemosit was later identified by The Standard as the officer wielding a gun and shouting “Utaona maajabu” (You will see wonders) during the abduction of Standard Media editor Alex Kiprotich. This same officer was captured on dashboard camera footage, his face and voice now familiar to millions of Kenyans who watched the terrifying video.

Despite this damning indictment and the DPP's finding that there was sufficient evidence to charge all seven officers, the case has since stalled, with no meaningful progress toward prosecution.