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State v. Pierce

Superior Court of Delaware

March 6, 2019


          Submitted: February 8, 2019

         Upon Defendant's Motion in Limine to Exclude Expert Testimony DENIED

          Annemarie H. Puit, Esquire, Matthew B. Frawley, Esquire, Jenna R. Milecki, Esquire (argued), Department of Justice, Wilmington, Delaware, Attorneys for the State.

          Eugene J. Maurer, Jr., Esquire, Elise K. Wolpert, Esquire (argued), Wilmington, Delaware, Attorneys for Defendant.


          The Honorable Andrea L. Rocanelli Judge

         This is a murder case. The State alleges that Defendant, Steven Pierce, shot and killed his girlfriend, Heather Stamper, on July 9, 2016 in her Delaware City home. The State proposes to introduce evidence tracking Defendant's movements for the 23-hour period before and after the approximate time of death. Defendant seeks to exclude the Google Wi-Fi Location Data[1] used to "geolocate" Defendant's cell phone on the grounds that the proposed evidence is not sufficiently reliable under the Daubert standard and would mislead and confuse the jury. The State argues that the technology at issue is reliable and would be helpful to the finder of fact. The reliability of Google's Wi-Fi Location Data is an issue of first impression in Delaware.


         Defendant was indicted by the Grand Jury on December 5, 2016, and charged with Murder in the First Degree and Possession of a Deadly Weapon During the Commission of a Felony for the intentional murder of Heather Stamper. The case was specially assigned to this Trial Judge. The trial was initially scheduled for January 2018 but was rescheduled when Defendant retained new counsel who was unavailable for that trial date.[2] A new trial date was set for August 2018.

         On June 5, 2018, Defendant sought permission of the Court to file two motions after the deadline imposed by the Court for pre-trial motions: a motion to suppress certain evidence and a Daubert motion. The Court did not address the motion to suppress because the parties reached an agreement that the State would not use the challenged evidence in the State's case-in-chief. Regarding the Daubert motion, the Court conducted an office conference on June 28, 2018, at which time it became clear that resolution of the novel issue involved would require that the trial date be rescheduled again. Accordingly, the Court conducted a hearing on July 6, 2018 to address Defendant personally regarding his right to a speedy trial.

         The Court found that Defendant's waiver of his speedy trial rights was knowing, intelligent, and voluntary. By Order dated July 6, 2018, the Court granted Defendant's Motion to File a Daubert Motion Out-Of-Time, over the State's objection. A new Trial Scheduling Order was issued, setting the date for trial as April 2, 2019, and setting forth deadlines for discovery and briefing in connection with Defendant's Daubert motion.

         The Court conducted a Daubert hearing on November 27, 2018. In support of the reliability of the State's proposed evidence, the State presented the testimony of Andrew Rist, an engineer, and Anthony Vega, a law enforcement officer. The State's two witnesses were subject to cross-examination by Defendant. The parties submitted post-hearing briefs.


         According to the United States Supreme Court, in 2018, there were 396 million cell phone service accounts in the United States.[4] The High Court emphasized that there are more cell phone accounts in the United States than there are people.[5] The most popular mobile devices have one of two operating systems that control the functioning of the phone. For Apple phones, it is iPhone Operating System ("iOS") and for Google phones and many other phone manufacturers, it is Android.

         Defendant's phone was a MetroPCS phone with the Android operating system. While there are similarities between Apple's iOS and Google's Android as it relates to capturing user data, the technology at issue in this case involves location data derived from communications between an Android mobile device and Google. (The data is referenced herein as "Google Wi-Fi Location Data"). Specifically, the subject of the Daubert motion in this case was the Wi-Fi-sourced geolocation information associated with a unique Google account transmitted from the Android operating system on Defendant's mobile device and stored by Google.

         A cell phone using the Android operating system serves as a data collection device as it continuously collects and sends information to Google as "events" approximately every 10-20 minutes. Meanwhile, other programs on the phone are running, either actively by the cell phone user, or idly in the background. These applications often rely upon Google Wi-Fi Location Data to customize information sent by Google to the user.[6] With each event, there are various categories of information sent back to Google, including the device's location history which is comprised of GPS, cellular data, and recognized Wi-Fi signals. Google collects and retains fairly detailed location information, including time-stamped barometer readings to determine the device's altitude, such as the floor within a building, and Wi-Fi scans recorded with a time stamp for each location, noting latitude, longitude, and estimated accuracy.

         Google Wi-Fi Location Data is not considered first-generation technology for geolocation. Global Positioning System ("GPS"), a utility owned by the United States government, uses satellites for positioning, navigation, and timing ("PNT") services.[7] GPS receiver equipment is found in many mobile devices, including cell phones and vehicle navigation systems. Mobile devices exchange signals with GPS satellites and use the transmitted information to calculate the user's position.[8] Under open skies, "GPS-enabled smartphones are typically accurate to within a 4.9 meter radius."[9] The accuracy of GPS can be compromised by many factors, including satellite signal blockage due to tall buildings or trees, indoor or underground use, and poor atmospheric conditions.[10] Nevertheless, the reliability of GPS is well established.[11]

         Another method for geolocation is Cell-Site Location Information ("CSLI"), which refers to the information collected as a cell phone connects to nearby cell towers.[12] Although cell site records are generated by cell phone service providers for commercial purposes, law enforcement agencies routinely request and use historical CSLI for criminal investigatory purposes.[13] With information from multiple cell towers, a technique called "triangulation" is used to identify the location of a cell phone, and by extension, the cell phone user's approximate location within 50 meters.[14] Like GPS, the reliability of CSLI is well established.[15]

         The underlying premise of Google Wi-Fi Location Data is the same as GPS and CSLI. A Wi-Fi positioning system relies upon Wi-Fi signals to determine the distance between the device and the signal access point ("AP"). Wi-Fi Access Points are the devices that create a wireless local area network, such as a router in an office, business, or home, by projecting a Wi-Fi signal to a designated area. Included in the location data sent to Google by Android devices are Wi-Fi scans, which include a list of the Wi-Fi APs the device could "see" at that particular time and location.[16]Generally, in order for a device to see a Wi-Fi AP, the device will be within 150 feet of a signal, much closer than with cell tower positioning. Google collects and stores the locations and strength of Wi-Fi APs, identified by their Media Access Control ("MAC") address, in order to locate mobile devices. When multiple signals are in range, Google Location Services uses multilateration to identify the device location, with more signals providing a more accurate location.

         Wi-Fi APs were first mapped by Google as part of its Street View program using vehicles which physically drove around with Wi-Fi receivers to collect street level pictures and record Wi-Fi signals, a process known as "wardriving." This mapping method was the subject of the Zandbergen paper published in 2004.[17] Since that time, Wi-Fi AP locations have been mapped and maintained by Google through a process called "crowdsourcing," whereby information sent back to Google by individual cell phones is used to identify the location of Wi-Fi APs.[18] Crowdsourcing allows more data to be collected more frequently and provides for greater accuracy as more users contribute to data regarding the location of Wi-Fi APs.


         Defendant's cell phone ("Target Device") was seized on July 9, 2016, the day Heather Stamper was found dead in her home in Delaware City, Delaware. The phone number for the Target Device matches the phone number that Defendant identified as his own phone number during his July 9, 20 1 6 interview with the police.

         Through a search warrant, [20] Detective Csapo of the Delaware State Police obtained Google location data for the Target Device, International Mobile Equipment Identity ("IMEI") number 359696076323056 ("Target IMEI").[21]Google responded to the search warrant in accordance with the Federal Electronic Communications Privacy Act[22] and provided the following information for each time-stamped event for the time period from 6:53 p.m. on July 8, 2016, through 549 p.m. on July 9, 2016: identity of account as; date; Universal Time Coordinated (UTC); date and time in Eastern Daylight Time (EDT) using military time; latitude; longitude; map display radius in meters; map display radius in miles; source (GPS or Wi-Fi); and device tag.

         Agent Vega analyzed the data associated with the Target IMEI and mapped the geolocation of the Target Device by plotting the latitude, longitude, and estimated radius of GPS and Wi-Fi coordinates, showing those locations using Google Earth. In addition to the Google Wi-Fi and GPS location data, Agent Vega used surveillance video to prepare a PowerPoint presentation tracking Defendant. Time-stamped photographs taken from video surveillance correspond to the Google Wi-Fi Location Data and GPS data to show Defendant and/or the Target Device travelling throughout this time period: in Heather Stamper's vehicle; driving on the streets of Delaware City and heading towards New Castle; at a check-out counter in a New Castle liquor store; driving towards Delaware City; in the vicinity of Heather Stamper's home; travelling towards and in the vicinity of Defendant's mother's home; with Defendant's mother entering a convenience store; and in various other locations nearby during the next day.


         The Delaware Supreme Court has adopted the Daubert standard to determine the admissibility of expert testimony.[23] Under this standard, the Court asks whether: (i) the witness is "qualified as an expert by knowledge, skill, experience, training or education;" (ii) the evidence is relevant and reliable; (iii) the expert's opinion is based upon information "reasonably relied upon by experts in the particular field;" (iv) the expert testimony will "assist the trier of fact to understand the evidence or to determine a fact in issue;" and (v) the expert testimony will not create unfair prejudice or confuse or mislead the jury.[24]

         When assessing the second factor of the Daubert standard-the reliability of the expert's opinion-trial courts consult a non-exclusive list offour more questions: (1) whether the opinion at issue is susceptible to testing and has been subjected to such testing; (2) whether the opinion has been subjected to peer review; (3) whether there is a known or potential rate of error associated with the methodology used and whether there are standards controlling the technique's operation; and (4) whether the theory has been accepted in the scientific community.[25]


         As the gatekeeper, the trial judge's role "is to make certain that an expert, whether basing testimony upon professional studies or personal experience, employs in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field."[26] Neither the parties nor the Court has identified a reported decision applying the Daubert standard involving testimony by a computer scientist or engineer addressing reliability of Google Wi-Fi Location Data.[27]Accordingly, this Court's reasoned analysis regarding the reliability of Google Wi-Fi Location Data is not informed by rulings of other trial courts.

         (i) The State's expert witnesses are qualified as experts by knowledge, skill, experience, training and education.

         Defendant does not challenge Andrew Rist as an expert in the computer science field. Rist has an undergraduate degree in mechanical engineering and a master's degree in manufacturing engineering, and has worked as an engineer for Oracle Corporation for more than 20 years.[28] Since 2008, Rist has been an Interoperability Architect reporting to Oracle's Chief Technology Officer, and his recent professional focus ...

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