United States v. William Julius, 14 F.4th 752

William Julius was convicted of two counts of arson for setting two fires at the building where his ex-girlfriend (Dawn Noack) was living after she rejected his advances.
Prosecution introduced text messages recovered from Julius’s cellphone showing repeated unwanted contacts and hostile messages; law enforcement extracted those messages and two witnesses testified about the extraction process.
Police found Julius shortly after the second fire hiding under a car with a lighter in his pocket and gasoline on his shoes and socks; firefighters detected gasoline and concluded an open flame likely ignited the combustibles.
The government did not formally tender the forensic witnesses as experts; the district court nonetheless instructed the jury that the witnesses gave opinion (but not expert) testimony about the cellphone extraction.
On cross-examination defense sought to explore location data from the phone (a 1:09 a.m. data point); the court sustained a government objection at an off-the-record sidebar and curtailed further questioning.
Julius appealed, arguing (1) the court erred by allowing non-qualified lay testimony about cellphone data extraction and (2) the court improperly limited cross-examination of the ATF agent about location data. The Seventh Circuit affirmed.

Issue	Julius's Argument	Government's Argument	Held
Whether testimony about cellphone data extraction required expert qualification under Rule 702/Daubert	Extraction testimony was expert technical evidence and should have required qualification and Daubert reliability analysis	Government did not tender the witnesses as experts; testimony was permissible lay/foundational testimony and Julius failed to object at trial	Reviewed for plain error; Julius conceded he cannot show witnesses were unqualified, so no plain error and conviction stands
Whether the court improperly cut off cross-examination about phone location data	Limiting cross-examination prevented him from showing he was ~1 mile away 12 minutes after first fire, undermining guilt	Any error was harmless because location data would not have made prosecution’s case significantly less persuasive	District court’s off-the-record sidebar ruling was procedurally dubious, but any error was harmless given overwhelming evidence of guilt; conviction affirmed

Daubert v. Merrell Dow Pharms., 509 U.S. 579 (1993) (trial courts gatekeep expert admissibility under reliability/Daubert framework)
United States v. Wehrle, 985 F.3d 549 (7th Cir. 2021) (police forensic testimony can be expert if it involves technical concepts beyond lay knowledge)
United States v. Montijo-Maysonet, 974 F.3d 34 (1st Cir. 2020) (cellphone data-extraction testimony held non-expert)
United States v. Brown, 973 F.3d 667 (7th Cir. 2020) (harmless-error standard for evidentiary errors)
Greer v. United States, 141 S. Ct. 2090 (2021) (sets forth plain-error review factors)
Rosales-Mireles v. United States, 138 S. Ct. 1897 (2018) (clarifies the fourth prong of plain-error review regarding fairness/integrity)
United States v. Nolan, 910 F.2d 1553 (7th Cir. 1990) (Court Reporter’s Act requires recording sidebar proceedings in criminal cases)