http://www.formula1.com/news/headlines/2009/4/9115.html
Seems like a pretty straightforward decision here. McLaren deliberately misled the stewards as to the nature of the incident, claiming that Trulli had just roared past without warning. This meant that Trulli got penalised. In fact, Hamilton had been instructed to, and indeed, voluntarily gave up the place back to Trulli, in which case no penalty should have been imposed on Trulli. Lying to the stewards is just not on. It should not happen and Hamilton and McLaren deserve this.