I have just been consulted on a complicated case that threw up a new question: is the illegal use of unauthorised information (Law 16B) a serious error (in the sense of Law 12C1(b))?
South dealt and opened 1♥, West overcalled 2♣, and North bid 3♠, intended as a splinter, but not alerted. East asked about 3♠ and was told it was natural and preemptive, and then passed. The auction continued to 5♥ doubled, making when West lead a ♠.
The TD found there was misinformation from the failure to alert/explain the splinter, that North/South had used unauthorised information to stop in 5♥, and East/West had used unauthorised information in leading a spade. A club lead would defeat 5♥. Without the misinformation and the use of unauthorised information by North/South, they would reach 6♥ doubled. East may have been able to show spades and attract the disadvantageous spade lead, so the TD adjusted for North/South 50% 6♥X-1, 50% 6♥X-2. We decided the spade lead against 5♥ was illegal and a serious error and was responsible for conceding 5♥X= rather than 5♥X-1.
| Result | Score | NS | EW |
|---|---|---|---|
| 5♥X= | +650 | 133 | 3 |
| ... | |||
| 5♥X-1 / 6♥X-1 | -100 | 15 | 121 |
| 6♥X-2 | -300 | 4 | 132 |
Adjustment for NS was 50%x15 + 50%x4 = 9.5MP
The damage due to the serious error was 118MP, so adjustment for EW was (50%x121 + 50%x132) - 118 = 8.5MP
