Susan Lacroix's Yerf -Dog go-kart was stolen from her driveway one evening when she went inside to have dinner. The thief placed an advertisement in the newspaper and sold it to Ronald Casey for half what it was worth. Later, Lacroix recognized the kart in Casey's yard and identified it as hers through its serial number.
In a suit brought by Lacroix for the return of the go-kart, Casey argued that he now had title to the kart because he paid for it without knowledge that it had been stolen. Is Casey's argument sound? Explain.