Elena Dementieva was beating Mary Pierce in the US Open Semi-Finals when Mary Pierce called for a 12 minute injury timeout. The only problem was that she wasn't injured. On the court she showed no signs of injury and her treatment basically was a 12 minute massage. This ruined Dementieva's momentum and allowed Pierce to compose herself. Pierce then when on to win the match.
Pierce did not break any rules although you can question her sportsmanship. Tennis clearly needs to make changes to their rules to prevent players from being deceitful to get a long time out.
What makes Pierce an ugly liar is her face and the post match press conference. I wish I had the video because her body language showed all the signs of lying. A quote doesn't do it justice, but here's some of her defensive remarks:
"No," she said flatly. "No, no, not at all. I mean, I'm 30 years old. I've been on the tour for 17 years. I don't believe in that. I don't think that that will make a difference.
"I believe at this level where we're playing, were all very good players, we're all very mentally strong. I had injuries that I needed to attend to, to help me. I was hoping that would help, that I could play better -- and I did. I just needed to do what I needed to do for my body and that was really it."
"Everybody gets injured," Pierce said. "There are timeouts for certain reasons. Some players go to the bathroom [90 second timeout]. Some change their clothes [90 second timeout]. Elena went and changed her clothes after I won the second set, so it's part of the game."