Probably, if you're referring to the second sighting. If I were the cops I'd comb the wooded areas at the corner of 48th and Randolph; the guy was headed in that direction when the motorcyclist spotted him. One is inclined to think that this person wasn't acting rationally, assuming he's the perp. Dressed in a t-shirt on a 45-degree night, walking right down the street with the kidnapped, possibly dead baby in his arms. A meth addict, maybe?
The last thing a meth addict is looking for is a dead baby to haul around (or a live baby). If there was indeed a man carrying Lisa around, it is a relative of Deborah or Jeremy, IMHO.