A dog handler who says her canine picked up Laci Peterson's scent at a California marina near where her body was found is due back on the stand today. Prosecutors are trying to prove Scott Peterson used the marina to dump his wife's body into the San Francisco Bay after killing her at their home in 2002. He has admitted to using the marina to launch a solo fishing trip on the day Laci disappeared, but denies killing her. Peterson's lawyers spent yesterday questioning the reliability of dog-tracking evidence. They say it's not a science and can't pinpoint exactly when a scent may have been left.