Evidently you didn't follow this case closely. They did find physical evidence. Laci's hair was found on a pair of needle nose pliers which was found in the boat.
Besides the circumstantial evidence points to none other but Scott Peterson.
Many people believe that circumstantional evidence doesn't carry the same weight as physical evidence. I've heard lawyers and prosecturos on some of the talking head shows say that a majority of convictions are based on circumstational evidence. I've also heard of the term "CSI Syndrome" where people who watch too many episodes of the show believe that there has to be a smokiing gun with bullet to match, or a bloody knife with the perps bloody fingerprints on it, or a hammer with the victim's blood and hair and the perp's fingerprints on it. Certainly after reading several crime books written by Ann Rule, it's pretty obvious that circumstational evidence carries a lot of weight. In at least one of the cases she's written about, no body was every found, but the circumstantial evidence was so powerful that there was a conviction.
Not only that Spunky, there were four spots of Peterson's blood on the bedroom quilt, the hair in the pliers, cement residue IN boat, on the boat cover, the CERTIFIED dog tracked Laci's scent to the END of the pier and then there was PETERSON'S OWN voice. Our troll above is simply talking NONSENSE. Almost ALL cases are mostly circumstantial. The DIRECT evidence of the bodies is about as direct as you can get. Don't even acknowledge this crap anymore.