West threw a spade, a subtle error, and South thought it over.

This card won the trick when West made a subtle error by playing low.

He then took full advantage of two subtle defensive errors.

So many subtle errors can be caused by that kind of boundary condition.

No doubt there was some subtle error of distortion in his work.

South won the opening spade lead and made a subtle error by leading the club king.

But experts in the field say plan participants are unlikely to detect subtle errors.

This demonstrates that West made a subtle error on the second trick.

Simon showed them how, taking advantage of a subtle defensive error.

Here it was a subtle error, for West kept the lead and shifted to the heart two.