BALTIMORE (AP) — One of the Baltimore police officers who arrested Freddie Gray has challenged police and a top prosecutor to produce a knife that prompted the arrest, arguing in a court motion that it is an illegal weapon. The motion appeared to challenge the basis for charges Nero faces after the arrest of Gray, a black man who died a week after suffering a severe spinal injury in police custody. Marc Zayon, Nero's attorney, argued in the motion filed Monday that the knife in Gray's pocket — described in charging documents as "a spring assisted, one hand operated knife" — is in fact illegal under state law. Many knives have these spring-assisted opening mechanisms but are not the automatic knives prohibited under Maryland law, said Michael Faith, marketing director for Henderson's Sporting Goods in Hagerstown. The Associated Press has made repeated requests to the police department for a physical description of the knife as well as photographs.