Slain Human Resource Manager at Wells Fargo Willis Onyango Ayieko died of head injuries.
Chief government pathologist Dr Johansen Oduor said the injuries led to bleeding to the brain.
“There was bleeding to the brain. Other than that there were bruises on the wrists caused by some cuffs found on him. There were also missing tissues on the mouth, ear and cheek,” he said.
He explained the missing tissues were a result of animal predation at the site where the body was found.
“They were caused by water animals like fish and crabs. We found a dead crab on the clothes. We think they were targeting the soft parts of the body,” he said.
Family pathologist Prof Emily Rogena was present.
She said they agreed with the findings.
The exercise was conducted at the Lee Funeral Home in Nairobi and was attended by the family, Siaya Governor James Orengo and MPs Sam Atandi and Elisha Odhiambo. Director of the homicide unit at the Directorate of Criminal Investigation Martin Nyuguto was present.
The autopsy will also form the basis of the case detectives are preparing.
A suspect linked to the gruesome murder was Monday arrested in Nairobi.
The arrest was made following a probe by multi-agency teams, police said.
The suspect was flushed out of his hideout in Nairobi's Dandora Phase IV Monday night, where he had rented a house using proceeds of the heinous crime, police said.
The suspect was placed at the scene of crime through forensic analysis, in the forensic-led investigation being conducted by a joint team of DCI's Homicide, CRIB and Operations detectives.
The investigation is ongoing with the team analyzing crucial leads to uncover and arrest other accomplices, the Directorate of Criminal Investigations (DCI) said.
Among those so far grilled include two M-Pesa agents who operate in Siaya.
This is after it emerged the killers of Ayieko withdrew money from his mobile phone through mobile banking.
The agents are supposed to help detectives identify the men who withdrew at least Sh100,000 in different locations in Siaya between October 19 and 20.
A team of detectives from Nairobi joined those on the ground on Thursday and announced they are pursuing good leads into his brutal murder.