Image copyright Reuters Image caption Joseph James DeAngelo appeared in court last week and was denied bail

A man accused of a string of murders, rapes and burglaries in California as the so-called Golden State Killer has been charged with four more murders.

Joseph James DeAngelo, 72, has now been charged with all 12 murders attributed to the serial killer.

The serial killer terrorised California residents in the 1970s and 1980s.

"Violent cold cases never grow cold for their victims or loved ones," Santa Barbara County District Attorney Joyce Dudley said at a news conference.

Mr DeAngelo was charged on Thursday with killing Robert Offerman and Alexandria Manning on 30 December, 1979, and with the 27 July, 1981 killings of Cheri Domingo and Gregory Sanchez.

Each of the first degree murder counts carries a maximum sentence of life in prison or the death penalty.

Image copyright Reuters Image caption The photo being held up shows murder victims Cheri Domingo and Greg Sanchez

The former policeman was arrested on 24 April at his suburban Sacramento home after investigators used his DNA to link him to the crimes through an online genealogy website.

In addition to the new charges, Mr DeAngelo has also been charged with four killings in Orange County, two in Ventura County and two in Sacramento County.

It is unclear where his trial will be held, and many questions about his arrest and alleged crime spree have yet to be answered.

A former investigator familiar with the case told NBC that he believes Mr DeAngelo may have been motivated by the breakup of an engagement to a woman in the 1960s.

Paul Holes, who retired from the Contra Costa County district attorney's office less than a month before the arrest, described the killer as "an anger retaliatory offender".

"We assumed that there had been some breakup in their relationship and that possibly caused him some angst," said Mr Holes.

Since his arrest, Mr DeAngelo has been held at the Sacramento County Main Jail medical unit. He is scheduled to appear in a Sacramento County courtroom on Monday.

Diane Howard, his court-appointed lawyer, says he will probably not enter a plea during the hearing.