[–] mynameispiff 0 points 2 points (+2|-0) ago 

Earlier this year his client had abandoned a Samsung Galaxy phone at a burglary crime scene, which allowed authorities to find the device, call 911 from the lock screen, and acquire the phone's actual number. Law enforcement soon determined the phone’s owner, Matthew Muller, and arrested him days later. But while executing that arrest, authorities found materials related to a separate kidnapping case reported earlier in the year.

I beleive any evidence uncovered during a legitimate arrest is usable in court. Since the arrest seemed to be legit, I see no issue with this.