Peter Chadwick is accused of strangling 46-year-old Quee Chadwick, to whom he was married for 21 years, after a heated argument on Oct. 10 of that year, the U.S. Marshals Service said.
According to a statement from the federal agency, Chadwick claimed at the time that his wife had been kidnapped and killed by a handyman, but police detectives who interviewed him "doubted his story, especially when they noticed scratches on his neck and dried blood on his hands."
The husband, a real-estate investor, was arrested by Newport Beach police on Oct. 11, 2012, and charged with his wife's murder.
WATCH: Newport Beach police chief discusses search for murder suspect
Members of the Marshals Service joined Orange County District Attorney Tony Rackauckas and Police Chief Jon T. Lewis at a Wednesday morning news conference, where they reiterated their vow to bring the fugitive to justice.
"Peter could be anywhere in the world," Lewis said. "He's got the financial means to avoid the restrictions placed on his travel and he's taken every opportunity to hide his tracks.
"We want to spread his picture and the story of his crimes far and wide," the police chief added.
After his 2012 arrest, Peter Chadwick was released on $1.5 million bail and appeared at 13 subsequent court appearances while staying with his father in Santa Barbara. Chadwick also surrendered his U.S. and British passports.
In 2015, he disappeared. According to investigators, Chadwick withdrew millions of dollars from his bank accounts. The father of three had allegedly read books about how to live "off the grid."
INTENSIFIED SEARCH: Millionaire murder suspect Peter Chadwick added to @usmarshalshq Most Wanted List. $100k reward offered for arrest. Chadwick fled while awaiting trial for 2012 murder of wife. @abc7 11am #abc7eyewitness pic.twitter.com/mYzW1F3b7l— Eileen Frere (@abc7eileen) September 19, 2018
Chadwick is being sought on a $5 million warrant. The Marshals Service is offering a $25,000 reward in the case, and $75,000 is being offered by the city of Newport Beach and private donors.
The Police Department is producing "Countdown to Capture," a podcast about the case.
Anyone with information about Chadwick's whereabouts is asked to call Newport Beach police at (800) 500-6273.