SAN DIEGO — With a simple Internet search, murder defendant Cynthia Sommer could have easily obtained the arsenic that appears to have slowly poisoned her Marine husband to death in February 2002.

But after three days of testimony from more than 30 witnesses, prosecutors have not presented jurors with any evidence that Sommer made a single attempt to secure the lethal poison.

Sommer faces life in prison without parole if she is convicted of murdering 23-year-old Sgt. Todd Sommer for his life insurance money. Prosecutors claim arsenic was an ideal poison choice: It is odorless, colorless and easy to obtain.

Special Agent Mary Jane Lewis, of the Naval Criminal Investigative Service, testified Wednesday that she paid $25 for seven vials of arsenic she found on eBay. She used her credit card and gave her home address for shipping.

Lewis is the third agent to testify how easy it is purchase the poison — in liquid or powder form.

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But Lewis conceded during cross-examination that her experiment certainly would have left an electronic paper trail from her computer's hard drive to her credit card statements and the eBay server. She admitted that she is still waiting to receive the seven-vial package, which she ordered on New Year's Eve. (VIDEO)

Prosecutors have no such trail linking 33-year-old Cynthia Sommer to arsenic.

Moreover, the case against her largely is built on the fact that, according to witnesses, she acted inappropriately for a grieving widow: She had loud parties at the couple's home on the Marine Corp Air Station at Miramar, Calif., in the weeks after Todd's death. She spent part of his insurance policy on breast implant surgery, exactly two months after he collapsed and died on their bedroom floor. She also began a relationship with another Marine the same day as her surgery.

Defense attorney Robert Udell told the judge during a sidebar Wednesday that he expects to present evidence that Todd Sommer was likely exposed to arsenic during a Feb. 8, 2002, visit with his supervisor and a colleague to the Naval Air Facility in El Centro.

The Marines' day trip, a preliminary site visit in advance of an exercise to be held outside the El Centro base, occurred the same day Sommer began complaining of gastrointestinal distress — and just 10 days before he died.

Outside the presence of jurors, Udell noted that El Centro is a known toxic waste dump area. (VIDEO)