Under prosecution questioning, Officer Garrett Miller said he and his accused partner Officer Edward Nero had chased Gray after being ordered to do so.
Gray's April 2015 death from a broken neck suffered in a police van triggered rioting and protests in the majority black city.
Prosecutors contend that Nero, 30, pursued Gray without probable cause and then failed to secure Gray in the van.
But Nero's lawyers argue that he had little to do with Gray's arrest and never touched him except when he tried to help Gray, 25, find an asthma inhaler.
Asked whether Nero had put handcuffs on Gray, Miller told prosecutor Michael Schatzow, "No, he did not."
Gray was bundled into a transport van while shackled and not belted in after officers found a spring-assisted knife in his pocket.
