People v. Peterson (California 2020) 2020 Cal. LEXIS 5539

PSD Scent Trailing Evidence; Reliability Foundation

In this high-profile murder of Peterson’s wife and unborn child, dog tracking evidence was at issue (along with a lot of other issues that aren’t pertinent to PSD teams). After extensive testimony from and cross-examination of various dog handlers concerning their training, as well as their dogs’ training and past performance, the court excluded all PSD scent trailing evidence except for evidence of scent trailing at the Berkeley Marina (the prosecution’s theory was that defendant killed his pregnant wife and then used his boat to dump her body overboard). The admitted evidence was that four days after victim’s disappearance, handler provided PSD with a glasses case with victim’s glasses inside and then gave a trailing command. Handler did this with both entry points into the marina. On one entry point, PSD did not react but on the second entry point, PSD “lined out, pulled her harness line taut, with level head and taking (handler) from an area near the parking lot down one of the marina piers to a pylon on the pier where a boat could have been tied, then given (handler) an ‘end of trail’ signal.”

Using the Malgren factors as modified in the Jackson case, the court held that admitting evidence of PSD’s trailing defendant’s wife’s scent was proper because the record showed that the handler was sufficiently trained, that the PSD was sufficiently trained and reliable, that the PSD was properly given an initial scent, and that some evidence tended to corroborate the trailing. Other requirements and theories put forward by defendant were shot down. The court also held that even if the PSD trailing evidence was excluded, the verdict would not have been affected. There were also objections to the jury instructions used for this evidence which were rejected.