Her body was discovered in a shallow grave in Macedon Regional Park over eight months later.
Last week, the Victorian Supreme Court ruled Borce Ristevski had purposely attempted to mislead police and conceal his actions before pleading guilty to manslaughter last Wednesday.
As reported by Daily Mail Australia, 55-year-old Ristevski told family and friends the authorities were listening to his phone calls and according to court documents he changed his mobile number twice in the months following Karen's disappearance.
In a call to a close friend, Ristevski is heard saying: "Make sure you don't say anything...don't tell them I spoke to you about anything nothing at all."
The father-of-two also told the couple's daughter Sarah not to trust police, declaring they "don't give a f**k".
He convinced her boyfriend to buy a new SIM card on his behalf so the purchase would not be traced back.
Prior to his admission on March 13, Sarah was revealed as a shock prosecution witness in the case against him.
He had long denied any involvement in Karen's death - claiming his wife had gone on a walk and never returned.
Ristevski will return to the Supreme Court of Victoria for a pre-sentencing plea hearing later tis month.