487 Mass. 448
Mass.2021Background
- On Sept. 15, 2015, a low-resolution residential surveillance video showed a Black man with long braids/dreadlocks in a red/pink shirt firing at a blue sedan; the shooter’s face was not discernible.
- A nearby civilian (Rock) heard gunshots and saw a Black man with thin braids and a red shirt running shortly thereafter but did not make a positive ID.
- Defendant Matthew Davis was on federal probation and wore a BI, Inc. ExactuTrack 1 (ET1) GPS ankle monitor; ET1 records location once per minute and purports to record speed.
- BI had formally tested the ET1’s location accuracy (circular error probability baseline in Colorado) but had not formally tested the ET1’s method for measuring speed; BI’s witness (James Buck) conceded no formal speed testing or known error rate.
- At trial the Commonwealth introduced ET1 location and speed data, the cell-phone recording of the surveillance video, and Rock’s testimony; Davis was convicted. The SJC reversed the convictions because admission of the ET1 speed evidence lacked proper gatekeeper foundation and was prejudicial.
Issues
| Issue | Commonwealth's Argument | Davis's Argument | Held |
|---|---|---|---|
| Admissibility of ET1 speed data (expert gatekeeper reliability) | GPS speed measures are reliable; device-level concerns were not significant enough to exclude speed evidence | ET1 speed methodology never formally tested; proprietary process, no peer review or known error rate — needs Daubert-Lanigan foundation | Judge abused discretion admitting ET1 speed evidence; speed testimony lacked proper Daubert-Lanigan or Frye foundation and its admission was prejudicial (convictions reversed) |
| Admissibility of ET1 location data | ET1 location was formally tested (circular error probability) and GPS location tech is generally reliable | Colorado baseline testing did not simulate urban multipath conditions; accuracy in Boston not established | Location data admissible: gatekeeper reliability satisfied by BI’s testing and baseline; any urban accuracy limits went to weight, not admissibility |
| Sufficiency of the evidence to identify shooter | Combined GPS (location and speed), video, and Rock’s testimony permitted a reasonable inference Davis was the shooter | Evidence was circumstantial and identification rested on inferences piled on inferences; video insufficient to ID | Evidence was sufficient when viewed in the light most favorable to the Commonwealth (but convictions reversed on speed-admission error) |
| Admissibility of maps / Confrontation & hearsay concerns (third-party mapping) | Maps and plotted points were computer-generated (lat/long and rendering) and not hearsay; no Confrontation Clause violation | Maps were produced by third parties and could be hearsay or testimonial without live testimony | Maps were computer-generated and therefore not hearsay; admission did not violate confrontation rights |
Key Cases Cited
- Daubert v. Merrell Dow Pharms., 509 U.S. 579 (setting nonexclusive reliability factors for scientific evidence)
- Commonwealth v. Lanigan, 419 Mass. 15 (adopting Daubert-like analysis for Massachusetts courts)
- Commonwealth v. Patterson, 445 Mass. 626 (gatekeeper function; new techniques require Daubert-Lanigan analysis)
- Commonwealth v. Camblin, 471 Mass. 639 (need for Daubert-Lanigan hearing on new device methodology)
- Commonwealth v. Camblin, 478 Mass. 469 (Camblin II) (review of post-hearing admissibility determination)
- Commonwealth v. Thissell, 457 Mass. 191 (GPS location generally reliable)
- Commonwealth v. Latimore, 378 Mass. 671 (standard for reviewing sufficiency of the evidence)
- Jackson v. Virginia, 443 U.S. 307 (federal standard for sufficiency review)