Sarah Wairimu Cohen widow to slain businessman Tob Cohen has accused her sister in law of filing in court a fake will.

Through lawyer Phillip Murgor, she claims they hired an expert document examiner who confirmed that the will was forged.

"Through an expert document examiner in a forensic report has confirmed that the said will is a blatant forgery and obtained through fraud," reads the petition.

In the application filed in court, Wairimu further seeks to cross-examine Gabriele Can Straten the sister in law regarding material aspects surrounding the alleged forgery of the will.

She also wants the court to disqualify Lawyer Danstan Omari and his law firm from representing the Cohen family arguing that they are conflicted as Omari is a witness in the murder case against her.