Amicus Brief: Julian Gallardo
State of oREGON V. juLIAN gALLARDO
Filing Date
April 24, 2023
Charge
Murder
Jurisdiction
Court of Appeals of the State of Oregon
Partners
Various forensic science professionals
Summary
Kate Judson joined various forensic science and legal professionals to file this amicus brief in the Court of Appeals of the State of Oregon in Julian Gallardo’s case to educate the court on issues surrounding the cell phone tracking data. We raise the issue around admissibility of ZetX Trax evidence which uses cell phone call detail records to create maps that supposedly show the phone's location at the time calls were made. Police officers used ZetX in this case to show the jury that Gallardo was at the location of the crime when it happened.
PRELIMINARY STATEMENT
The prosecution in this case relied on evidence developed from a computer software program called ZetX Trax, which uses a cell phone’s call detail records (CDRs) to create maps supposedly showing the phone’s location at the time calls were made. Two police officers entered the defendant’s CDRs into ZetX, showed ZetX maps to the jury, and gave their opinions about the defendant’s location around the time of the crime. One witness said that, in his opinion, the defendant was at the crime scene before, during, and after the crime, and was traveling with his co-defendant to other locations around the same time. Another law enforcement witness said the locations shown by the ZetX maps created a “high likelihood” that the defendant and co-defendant were moving together, and said the ZetX maps were consistent with the defendant being at the crime scene around the time of the crime.
Though the task ZetX performs requires complex science, ZetX has been developed, implemented, and used extensively in court without following the traditional procedure for scrutiny by the scientific community, and the limited scrutiny by scientific experts has resoundingly rejected the validity of ZetX. The basic function ZetX performs reconstructing a cell phone’s location based on historical CDRs—involves scientific principles that fall within the discipline of radio frequency (RF) engineering. To do what ZetX claims to do requires a complicated analysis of technical issues involving how cell phones and cell towers transmit radio waves. At the technical level, the details are beyond the comprehension of laypeople, requiring knowledge of mathematical and scientific principles mastered only by extensive scientific training or experience. As a computer software program, ZetX also necessarily involves extensive computer software engineering.
Despite its reliance on complex science, ZetX has not been subjected to traditional scientific scrutiny. ZetX has not been supported by peer reviewed publications, nor has ZetX publicized technical documentation as to how its computer software program performs the complicated analysis required by the task. Rather, the ZetX algorithm remains proprietary and unavailable to public scrutiny by scientists. ZetX also has no scientifically established error rate, which is another crucial factor for admitting scientific evidence.