How do you detect cheating in Chess?

Shaterri writes: Which is more likely: that a low-ranked player could play through a high-level tournament at grandmaster level, or that they were getting undetected assistance from a computer? How about when that player is nearly strip-searched with no devices found? How about when their moves correlate too well with independent computer calculations? Ken Regan has a fascinating article on one of the most complex (potential) cheating cases to come along in recent memory.