| DR. RALPH CHENG Senior Research Hydrologist U.S. Geological Society |
Mon, Oct. 04, 2004 Scientist: Laci's body likely dumped near Berkeley Marina An expert on tides and currents testified that based on wind and tidal information the pregnant body of Laci Peterson was likely dumped just between the Berkeley Marina and Brooks Island -- the general location Scott Peterson said he was motoring his fishing boat the day she disappeared. Ralph Cheng, a hydrologist with the U.S. Geological Service who has studied the bay for 30 years, said he came up with that location after back- tracking from where the bodies washed up after a storm in mid-April 2003. Cheng's testimony is critical for the prosecution because it places Peterson, who is charged with two counts of murder, where Cheng theorized the bodies were dumped just before Christmas 2002. Defense lawyer Mark Geragos tried to undermine Cheng's testimony, pointing out that although Cheng studies tides and currents, he has never studied how a body moves under water. Cheng cautioned that that was the "highest probability" location. "Can you predict with any certainty within inches or feet where these bodies would have started from?" asked prosecutor Dave Harris. "No, I'm afraid not," Cheng replied. "I don't know how a body behaves in water,'' Cheng conceded. "I've done particle tracking, not bodies.'' "You've never done any study of bodies or anything of that size?'' Geragos asked. "That's correct.'' Cheng also conceded that his findings were his "best guess'' based on his knowledge of tides, currents and wind. "It's just probable, not precise?'' Geragos asked. "That's correct,'' Cheng said. Geragos also pointed out that Cheng's report to Modesto police focused on the trajectory of the body of the male fetus that washed ashore, not of Laci Peterson's body, which was found about a mile from the baby's. He acknowledged that he could not reproduce the trajectory for Laci's body, only a possible path for the fetus, because it was lighter and unencumbered. "You're trajectory did not work for Laci Peterson?'' Geragos asked. "That's correct,'' Cheng said. Under further questions from Prosecutor Dave Harris, Cheng explained that Laci's body might have reacted differently to the currents than the baby because Laci's torso was heavier than the baby's and may have been weighed down longer than the baby. Prosecutors believe the baby separated from the mother when the top of Laci's uterus decomposed, and the baby began to drift with the current, landing onshore. "If she was weighed down, would that make her properties in the water behave differently?'' Harris asked. "It would,'' Cheng said. On cross-examination, Geragos attacked Cheng's findings as "assumptions." "Most scientific information is based on assumptions," Cheng said. The prosecution is expected to rest its case Wednesday or Thursday. The defense will begin its case on Tuesday, after a Monday court holiday. TIDE INFORMATION IN "PLAIN ENGLISH" HOME INDEX LACI SCOTT TRIAL PG 1 PG2 ALIBI-WITNESS LIST WIRETAPS EVIDENCE PHOTOS |
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