Chevron South Africa CEO Stephen King pleaded not guilty Thursday to five felony charges alleging he forged his late wife's signature on her will after she died of lung cancer, thereby receiving all of her more than $1 million estate. King, 58, of Danville, is charged with falsifying a will, grand theft and three counts of perjury in a case exposing a bitter probate feud between King and the family of his late wife Jeanette Elaine King, also a high-ranking executive in the San Ramon-based oil company.