Woody Vann told ABC11 that Mangum sent him a fax from the Durham County Jail, asking that he remove himself from her case.
Mangum is charged with stabbing her boyfriend, who later died.
Vann said he'll file a motion requesting to be removed from the case Tuesday. However, the judge has the final say.
There could be a hearing over the matter, or a judge could issue an order.
If Vann is removed, it will be the third lawyer requesting to be taken off Mangum's case.