A 31-year old mature student, Wamalwa is still harassed by the police and still suffers pain from the beatings he received in prison last year. But he has not been cowed into silence.
His case forms part of the damning evidence Amnesty International has amassed against the Kenyan government. Torture of political prisoners and criminal suspects occurs routinely in Kenya, says Amnesty.
Mr Wamalwa - for his security he has asked that a fictitious name be used - was arrested at his home in western Kenya early last year. After being held in solitary confinement, he was taken one morning to a room where he was stripped and tethered. There, a group of men in suits interrogated him about membership of a guerrilla movement and about importing arms from Uganda.
"Over the following days I was beaten with sticks on the thighs and buttocks," says Mr Wamalwa. "I was also beaten very hard on the ears and once on my genitals until I bled. The warders got scared when they saw the blood and one day a man in a white coat came and gave me an injection.
"Back in the interrogation room, I was made to lie down naked with my legs in the air while they hit my joints. In the cell I was prevented from sleeping and I could hear the cries of other prisoners."
After two weeks of maltreatment, Mr Wamalwa confessed to membership of FERA, an insurgency movement whose existence has never been proved by the authorities. He also admitted to a murder and to a train derailment which, it later transpired, had never occurred.
The charge of FERA membership was subsequently replaced by that of murdering two policemen. After six months in detention, in very harsh conditions, all charges were dropped. He was released in August.
"Many of those tortured are involved in grass-roots opposition politics," says Dr Ling Kituyi, who has treated Mr Wamalwa and dozens of other torture victims at her clinic in Nairobi. "The torture is systematic and often continues after a confession has been extracted. Most people are too scared to seek legal redress or even medical treatment."
Dr Kituyi is Norwegian, married to a leading Kenyan opposition politician. She says common symptoms in torture victims include hearing and urinary problems, fractures and abdominal hernias.
Most of her torture patients come from an area of western Kenya which the ruling Kanu party declared its own in the wake of politically-instigated ethnic clashes in 1992.
Last year, scores of people in that region mysteriously disappeared. Many had been arrested; others went underground to avoid being picked up.
The Bungoma Professionals Group, of which Dr Kituyi is a member, has publicised these detentions and has helped secure the release of a few, though an unknown number are still being held.
In some cases where the authorities have been unable to make charges of sedition stick, detainees have been released only to be rearrested on criminal charges.
"Common torture methods," says Dr Kituyi, "include the application of electric wires to genitals, immersion in water-filled pits and confinement in cold storage until paralysis sets in."
The location of the interrogation centres is unknown. The Kenyan government denies their existence.
"Torture and beatings are an integral part of the police culture," says Maina Kiai of the Kenya Human Rights Commission. "There has been no condemnation of police who routinely beat up people."
Those who do speak out can find themselves censured. A magistrate who dismissed a case on the grounds that confessions had been extracted under duress, and who ordered an investigation of the police involved, was transferred away from the capital to a remote country area.
Amnesty International has called on President Daniel arap Moi's government to curb illegal police practices and to ratify the United Nations Conven- tion against Torture.