Laci Peterson had caffeine in her system when she died, a toxicology report shows, while her unborn son, Conner, did not, a source familiar with the tests said.
Toxicology documents also show that police specifically asked medical examiners to test Peterson's remains for the "date rape" drug GHB, and that none was found.
"Toxicology testing performed on skeletal muscle is positive only for caffeine and PEA (decomposition product)," according to a report from the Contra Costa County coroner's office, the agency that performed the autopsies.
The presence of caffeine in Peterson's body and not in her unborn son's does not, however, indicate that Conner was outside his mother's womb when she was killed, forensic analysts said.
Attorneys for Scott Peterson, who is charged with murdering his wife and son, may try to use the toxicology tests to raise questions about the circumstances of the deaths, experts speculated.
Prosecutors maintain that Peterson murdered his wife on Dec. 23 or 24, when she was nearly eight months pregnant, and then pretended she was missing while a massive search ensued.
Laci's and Conner's remains were found in mid-April about a mile apart along the eastern shore of San Francisco Bay, within four miles of the spot where Peterson told police he launched his boat for a solo fishing trip on Christmas Eve.
Peterson's defense team maintains that authorities mistakenly targeted the 30-year-old fertilizer salesman, floating theories that include cult members and a suspicious van -- and casting doubt on whether Peterson killed his wife in the days before Christmas.
Evidence suggesting that Conner was born before he was killed would aid the defense, said Stephen Schoenthaler, a criminal justice professor at California State University, Stanislaus.
That is because Peterson would appear to have had little opportunity to kill while under the police and media scrutiny that developed soon after he told family members that his wife was missing.
"It all comes down to how much (caffeine) was in her, and was it a reliable measure," Schoenthaler said.
Three forensic experts said it would be uncommon to find measurable amounts of caffeine in the body of an unborn child even if its mother consumed large quantities of it. That would suggest that the Peterson test results are meaningless.
"Trace amounts can get through, but trying to find it for a toxicology (report) is an exercise in futility," said forensic pathologist Dr. Harry J. Bonnell of San Diego. "The odds of it passing into the fetus are minimal to nil."
Dr. Mary Case, chief medical examiner in St. Louis County, Mo., and an expert in child death, frequently reviews toxicology reports on fetuses whose mothers are suspected of substance abuse. She said she has never seen an unborn child with measurable amounts of caffeine.
"In the usual amount of caffeine that people have, it just wouldn't show up (in a fetus)," Case said.
Dr. Richard T. Mason, forensic pathologist for the Santa Cruz County coroner's office, said the placenta is more effective in blocking out caffeine than other chemicals, such as cocaine.
Caffeine can stay several days in the body of an adult after consumption, Bonnell said. Common sources are coffee, tea, sodas, chocolate and some over-the-counter medication.
Friend: Caffeine was avoided
Laci Peterson, a 27-year-old substitute teacher, enjoyed coffee but avoided the beverage -- and its caffeine -- when she was pregnant, said a friend who asked to remain anonymous.
"She had tried to limit or stop drinking caffeinated drinks," the friend said. "She did drink coffee before she became pregnant."
Bonnell acknowledged that members of Peterson's defense team could attempt to show that Laci consumed something with caffeine after giving birth.
"The world could also end tomorrow," Bonnell said. "They can blow smoke with it, but the fact that it was not in the baby certainly is not proof that the baby had to have been born."
Mason also noted that Laci Peterson would have had multiple opportunities to ingest something with caffeine in it.
"If she was home alone and had a cup of coffee or cup of tea, who's to say?" Mason asked. "I'd be hard put to make something out of that."
In asking for the GHB test, police investigators sought evidence of the depressant that can render people unconscious, particularly when mixed with alcohol.
In low doses, gamma hydroxy butyrate produces a high or euphoric feeling as inhibitions are depressed, making it a popular drug in the club scene.
Mason said that if the drug had appeared in this case, it could have been an indication that Peterson had been drugged in an attempt to subdue her before she was killed.
"That would be the obvious inference," Mason said. "I don't know why they looked for that, unless they had some indication that he had access to it."
GHB metabolizes rapidly in the system and can be hard to detect during testing, Mason said.
"It's pretty difficult to find, even in a case where it's been used," he said. "I don't think decomposition would enhance the ability to find it, certainly."
Bee staff writer John Coté can be reached at 578-2394 or firstname.lastname@example.org.
Bee staff writer Garth Stapley can be reached at 578-2390 or email@example.com.