SAN JOSE — Lawyers for Oracle Corp. pulled no punches on Monday in trying to undermine the credibility of a former White House economist who testified that Oracle cost Hewlett Packard more than $3 billion by breaching a software contract.

The testy cross examination came roughly three weeks into a trial in which HP accuses Oracle of reneging on a pledge to continue developing software for HP servers that use the Itanium microchip. HP says that Oracle’s 2011 announcement that it would cease support decimated its Itanium business.