A driving instructor was charged after splashing a police officer when he drove through a puddle.
Community leaders in Blackburn, Lancashire, have criticised the decision to prosecute Tahir Mahmood at an estimated cost of £20,000.
He was charged with driving without consideration for other road users in November 2003 but cleared this month.
The Crown Prosecution Service defended its actions, saying a witness had claimed Mr Mahmood did not slow down.
The case involved two hearings and Mr Mahmood, of Blackburn, faced the prospect of a £2,500 fine and the addition of points to his clean driving licence.
It is believed he changed lanes near to Blackburn Rovers' Ewood Park stadium and sped through the puddle.
Court summons
He was later stopped by a traffic officer and claimed in court he had offered an instant apology.
He was summoned to court on a charge of driving without consideration for other road users seven months later, but magistrates found him not guilty.
A Crown Prosecution Service spokesman said: "We cannot confirm the cost of the case, but can confirm that our involvement began in June of this year.
"A summons was issued on April 29 and there was no consultation with the CPS prior to the first court appearance."
He said a witness statement provided had been considered enough to take the case to court, adding: "It was in the public interest to proceed."
"Magistrates made no criticism of the CPS and had decided that there was a case to answer."