Forensic expert tells court Tob Cohen’s disputed signatures were forged

Forensic document examiner John Muinde before Kibera High Court Justice Diana Kavedza on November 11, 2026. (Photo: Handout)

A forensic document examiner has told the High Court that signatures allegedly linked to murdered Dutch businessman Tob Cohen were imitations, raising questions over the authenticity of documents bearing his purported handwriting.

Testifying in the murder trial of Cohen’s widow, Sarah Wairimu, forensic document examiner John Muinde told Justice Diana Kavedza at the Kibera Law Courts that his examination of three disputed signatures revealed characteristics consistent with simulated handwriting.

Muinde, who testified as Prosecution Witness 27 (PW27), explained that the signatures marked N, P and Q appeared to have been made by someone attempting to reproduce Cohen’s handwriting rather than by the businessman himself.

He told the court that forensic examination relies on identifying individual writing characteristics that are difficult to reproduce accurately.

Invoking the forensic principle of individuality attributed to Dr Paul Kirk, Muinde explained that every object, whether natural or man-made, has distinctive characteristics that distinguish it from others.

“The person who appended the questioned signatures appeared to have attempted to imitate Cohen’s individual handwriting characteristics,” he testified.

The examiner explained that signature forgery often involves studying and practising an original signature before attempting to reproduce it.

However, he said, close examination can expose an imitation through subtle differences in pen movement, letter proportions and structural formation.

Using enlarged images, Muinde demonstrated how he compared the questioned signatures against Cohen’s known signatures, focusing on the freedom of pen movement, relative proportions of letters and the overall structure and size of the handwriting.

He told the court that such differences can help establish whether a signature was genuinely written by an individual or simulated by another person.

The testimony forms part of the prosecution’s evidence in the case against Wairimu, who is accused of murdering her husband.

Earlier, the court heard how investigators began searching for Cohen after the Netherlands Embassy reported him missing in July 2019.

Former Kilimani Sub-County Criminal Investigations Officer Fatuma Hadi Ali testified that when she contacted Wairimu, she maintained that her husband had travelled to the Netherlands for medical treatment.

When investigators questioned her about his prolonged absence and inability to establish the airline he had used, she reportedly reassured them: “Don’t worry. I know he is in the Netherlands for treatment and he will be back.”

The court also heard how Cohen’s body was eventually recovered from a septic tank at a property in Lower Kabete on September 13, 2019.

The body was wrapped in a black bedsheet, tied with manila ropes and covered with a polythene bag, with the head bound in a red bathrobe.

Cohen’s sister, Gabrielle, subsequently identified the body before it was transferred to Chiromo Mortuary.