Johannesburg - One of the criminal trials against forensic investigator Paul O'Sullivan was interrupted on Friday by an application for the magistrate to recuse herself because she is allegedly the aunt of President Jacob Zuma's son, Edward Zuma.Randburg Magistrate Ndivhuwo Sethusha denied the application, saying her relationship with Zuma was distant.O'Sullivan has opened numerous cases against Edward Zuma over the years. Zuma has publicly stated he believes the investigator is a "foreign agent", is an enemy to the country, and should be deported.O'Sullivan and Melissa Naidu have been appearing in the Randburg Magistrate's Court on charges of kidnapping, fraud, and extortion.They allegedly took Cora van der Merwe from her offices at law firm Ronald Bobroff & Partners Incorporated to obtain a statement about a leak of documents from the company.READ: Paul O'Sullivan case dismissed, witnesses poor, says magistrateMassive fraudThe leak eventually led to massive fraud being uncovered in the law firm, the Bobroffs fleeing to Australia, and finally being disbarred from practising law in this country.Van der Merwe never revealed any of this to O'Sullivan or Naidu, who were executing their mandate as appointed by Darren Bobroff.This was despite her stating she had already made "disclosures in terms of the Protected Disclosures Act" to then Moneyweb journalist Tony Beamish and an advocate, Schalk van der Sandt.O'Sullivan and Naidu have said in their court submissions they regard the case as malicious prosecution.Earlier this week, the defence applied for the case to be dismissed, saying that Van der Merwe contradicted herself under cross-examination.Prosecutor Jabulani Mlotshwa was about to argue against the application when defence advocate Zirk Pansegrouw applied for Sethusha to recuse herself.Pansegrouw said the application had nothing to do with what had transpired in court, but was based purely on her relationship to Zuma.He said O'Sullivan discovered the relationship on Thursday night.READ: Ntlemeza's daughter threatens to kill cop who opened case against fatherRelationshipSethusha is married to Justice Jeremiah Shongwe. Shongwe's sister, Minah Shongwe, is the Edward Zuma's mother. That makes Sethusha the aunt of Edward Zuma, he explained.Pansegrouw said the relationship raised the reasonable apprehension of bias in the trial."My husband is not a relative of the president," Sethusha said."We don't have a relationship with him. This is a distant relative and unless you put forward another reason I will not allow this to go further. I was not even aware there were cases opened against him by the accused. I do not speak to him about this. This relationship is too far removed. We are not related," she said.Mlotshwa then argued why he believed the court should dismiss the application to have the case thrown out.He said the credibility of the witness could only be cast into doubt if her testimony was extremely poor. The accused had to answer to the charge of extortion as they had put pressure on the Van der Merwe, he said.They "committed the crimes to get money from the complainant's employer". Mlotshwa said the application was a fishing expedition and the defence had not pointed out the contradictions in Van der Merwe's testimony.Sethusha said it was premature for both sides to attack the evidence at such an early stage in the trial. She dismissed the application.The trial will continue on September 4.