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Richmond-San Rafael Bridge toll collector Deborah Ross, seen in a family photo, was killed in 2009 at the Richmond-San Rafael Bridge toll plaza, along with Ersie Charles Everette, a bus driver for the Golden Gate Transit Authority. (Family Photo)

MARTINEZ -- Richmond-San Rafael Bridge toll plaza killer Nathan Burris has a history of threatening to kill people, namely his past employers, according to testimony in the opening day of a penalty trial that could result in a death sentence for the Richmond man.

Burris, 49, was convicted Wednesday of capital murder charges in the jealousy-fueled Aug. 11, 2009, shotgun slayings of his ex-girlfriend, 51-year-old Caltrans toll taker Deborah Ann Ross, and Ross' friend, Golden Gate Transit bus driver Ersie "Chuckie" Everette, a 58-year-old San Leandro resident.

In the trial's penalty phase, the prosecution is presenting evidence to convince the jury to recommend that Burris be sentenced to death instead of life in prison without the possibility of parole.

Burris, who is acting as his own attorney and frequently laughs in court, told jurors to "flip a coin," he's fine with either potential fate.

"I'm as cool as a cucumber -- there's no problem," Burris said in his opening statement Thursday.

Two of Burris' most recent employers, Kentucky residents Frank and Linda Keichline, testified that they fired Burris for incompetence in 2008 after he racked up thousands of dollars in damages while working as a cross-country trucker for their business, Safe Way Auto Transport.

They kept Burris' toolbox for collateral for the $9,300 he owed them, leading him to make a series of threatening phone calls that had the married couple living in fear.

"I'm willing to lose my life for my (expletive). Are you willing to lose your life for my (expletive)?," Burris said in a voice mail to the Keichlines that was played for the jury.

The phone calls prompted the Keichlines to send Ross a letter in November 2008 warning her about an "unpredictably and, sort of, unwinding, that we were seeing with Mr. Burris that may be a threat to her personally," Frank Keichline said.

Linda Keichline said she was so unnerved by Burris' threats that she began keeping a pistol in an office desk drawer and went to a range for target practice.

"Why did you come here from Kentucky, to say ha-ha?" Burris asked Linda Keichline.

"I feel you're a very dangerous man, and that's why I came here, to testify to that," she replied.

Chief Assistant District Attorney Harold Jewett told jurors he will present evidence that Burris also threatened to shoot and kill managers and staff at a rental office when Burris worked as an armed security guard at an Oakland housing complex in 1993. The incident resulted in misdemeanor charges by the Alameda County District Attorney's Office, despite Oakland police pushing for a felony complaint.

Testimony continues Tuesday.

Contact Malaika Fraley at 925-234-1684. Follow her at Twitter.com/malaikafraley.