Before beginning deliberations Friday, they were confronted during closing arguments with the same question by attorneys for both the prosecution and defense: How does someone who just murdered their spouse behave?
With no smoking gun to show that Sommer was the source of the arsenic detected in her husband's liver, both sides depended heavily on circumstantial evidence to sway the Superior Court jurors.
Prosecutors argued that Sommer wanted more than she could afford on the $1,700 monthly salary Sgt. Todd Sommer brought home, and saw the military life insurance policy as a way to "set herself free."
Sommer's friends and co-workers testified during the trial that Sommer threw wild parties, got her breasts enlarged and had casual sex with multiple partners in the weeks after her husband's collapse.
But, reports The Early Show national correspondent Hattie Kauffman, defense lawyers stress there's no physical evidence linking Sommer to the arsenic found in her husband's body, and they say the 911 tape shows she was trying to save his life.
Deputy District Attorney Laura Gunn asked jurors to use their common sense to find Sommer guilty.
"The defendant has wrongly imagined that if no one could tie her to the poison, she could never be prosecuted," Gunn said. "She gave the general impression of a grieving widow but certain things she said or did betrayed her."
Sommer, 33, sat quietly in a taupe pantsuit, occasionally taking notes or whispering to her attorney's assistant during the daylong closing arguments.
She nodded slightly as defense attorney Robert Udell recounted for jurors how she had gone home and cradled her toddler son while staring at a picture of her dead husband on the day of his collapse.
"The things she did were consistent with innocence," Udell said. "Not a thing consistent with guilt."
Earlier, Gunn argued that Sommer, who worked a minimum-wage job at a Subway restaurant, had an "ah-ha" moment in early 2002, shortly after her husband's small trust fund ran out.
Rather than living within her means, Gunn said, Sommer decided to poison Sgt. Todd Sommer with arsenic in order to cash in on his $250,000 military death benefit.
"She may have been crying and acting upset and tearful, but the best evidence of what was going on in her head is what came out of her mouth," Gunn said, reminding jurors that witnesses testified the defendant asked about the life insurance and tax loopholes just hours after the Marine collapsed and died in their home Feb. 18, 2002.
"What was going on up here and in here," Gunn said, pointing to her head and heart, "was a big calculator."
Co-workers testified during the trial that the new widow didn't grieve quietly in the weeks after her husband's death but, reports Kauffman, the defense said she was simply in a vulnerable state.
Jurors heard plenty of colorful evidence about her spendthrift ways and party lifestyle, but less evidence was presented actually linking her to the arsenic.
Gunn recognized in her argument that she did not have a "hard, demonstrable link" to prove Cynthia Sommer bought arsenic or gave it to her husband, but asserted that the defendant was the only person with the motive and access to poison the Marine.
Cynthia Sommer, 33, has pleaded not guilty to first-degree murder with special circumstances of murder by poison and for financial gain. She faces life in prison if convicted.
Todd Sommer was in top condition when he died at the couple's home on the Marine Corps' Miramar base in San Diego.
He had spiked a 103-degree-Fahrenheit fever days earlier, but his widow testified that he was well enough that weekend to drink beer during a family trip to the Knott's Berry Farm amusement park in Orange County.
His death was initially ruled a heart attack. Tests of his liver later found levels of arsenic 1,020 times above normal. Expert witnesses for the defense raised questions about why arsenic wasn't detected in similarly large concentrations in his other tissues.
Cynthia Sommer's in-laws testified that she objected when they asked her to put her husband's $250,000 death benefit in trust for herself, their baby and her three children from a previous marriage.
She cried when called to the stand Jan. 17, dabbing her eyes as she recounted her husband's final moments.
But she also said during cross-examination that she hadn't been able to envision her future with the Marine. The pair married in 1999.
She is now engaged to a former Marine she met two months after her husband's death. She was extradited last March to California from her current home in West Palm Beach, Fla.