Wechuli, a traditional healer who lived in Kawangware, Nairobi, went home with his girlfriend of four months, Jane Kadogo Mutiso.
Sometime after they had retired to bed, Wechuli who lived with his two children, called his daughter and asked her to bring him a knife.
Moments later, the neighbour's daughter heard the healer telling someone to kneel down and ask for forgiveness.
Overcome by curiosity, the girl peeped through a crack in the door and saw the two, naked, with the man directing the woman to close her eyes.
He was holding a knife at the time.
The girl ran over to her mother and recounted what she had seen, when they saw the man and his two children, without the woman.
This prompted mother and daughter to go back peeping and using a torch, they saw a leg.
They called on the watchman, who in turn called the landlord's son who broke the padlock to Wechuli's house.
Once inside, they were shocked to find a woman's headless and naked body. Kadogo's stomach was cut, exposing her intestines.
There was a knife next to the body.
After seeing this, the witnesses reported the incident to the Muthangari police station.
When the police visited the scene, they found Kadogo's head placed in a basket. There was also a calabash with other ritual materials including a feather, twigs and sorghum sticks.
The bloodied knife was placed beside the body.
A postmortem showed that the cause of death was neck and abdominal injuries due to sharp force trauma. The DNA analysis showed that the body and head matched Kadogo's.
Later on, Wechuli was arrested after presenting himself to the police station.
He was transferred to Kabete Police Station and then to Mathari Hospital for mental assessment.
The doctor concluded that the man's mental state was normal and the trial began with the prosecution producing 11 witnesses.
When put on defence, Wechuli claimed that he did not intend to kill his lover.
He said they were making love when he felt tired and nauseated but Kadogo insisted they continue.
He felt pain and lay on her chest whereupon the lady's voice changed to that of an epileptic person.
The High Court heard that Wechuli then saw a big hand coming towards him and himself holding a big knife which he used to cut it.
He saw himself in a desert, a corrugated house and light, and on looking down he saw a vision of a headless body and thereafter the head in his hand.
Wechuli said he actually saw he had a head in his hand and he threw it and gathered his children telling them to go to their mother’s place in Kibera.
On the way to the bus station, he added that he felt the smell of alcohol and was nauseated.
After dropping off his children, Wechuli went back to his house he found a crowd with a woman saying "the grandfather has killed somebody."
Wechuli went on to state that sometime in 1986, he was a mental health patient, but he was treated and cured traditionally.
"According to him, if he was in his right mind, he would not have murdered the deceased. He pleaded that he had no intention of committing the offence," court documents read.
The trial court held that all the circumstances portrayed a man who knew exactly what he was doing and his intention to cause death was quite obvious.
He had also not established the defence of insanity.
On March 8, 2017, the court proceeded to convict and sentenced him to suffer death.
Wechuli moved to the Court of Appeal arguing that the trial judge erred in law by failing to properly consider his mental state during the commission of the offence.
After reviewing the case, the court found that the prosecution had applied to have Wechuli undergo a further examination, which was granted.
This came after his father said his son had suffered from a mental illness when he was 12 years old.
The mental examination, however, never took place.
For the defence of insanity to be held, the accused person must prove that he was of unsound mind, strictly, at the time the crime was committed.
Appellate judges Asike-Makhandia, Agnes Murgor and Ngenye-Macharia went through the chronology leading to Kadogo's murder and concluded that the man was sane.
"The appellant was still cognizant and conscious enough to know what he was doing and that it was wrong. His actions after beheading the deceased betray him all the more," they said.
"The insinuation that he suffered from a mental illness when he was 12 years old remains nothing more than a mere unsubstantiated statement."
The judges held that Wechuli was mentally fit when he killed his girlfriend and dismissed his plea.
The appellate court found that the prosecution had proved its case beyond reasonable doubt and upheld the trial court's decision.
"Accordingly, there is no basis to warrant our interference with the sentence meted by the trial court. In the upshot, we find that the appellant’s appeal is without merit and the same is hereby dismissed in its entirety," the judgement delivered on September 22, reads.