A 44-year-old Fairfax County man who was charged three times during a 24-hour period with driving while intoxicated has been convicted of the offenses, sentenced to one day in jail and had his driver's license suspended for 5 1/2 years.

A new Virginia drunk driving law requires a mandatory two-day jail term on the second offense and a 30-day mandatory jail term on the third conviction. The defendant, James D. Block of 8504 Zephyr Dr., in the Alexandria area of the county, was not subjected to the mandatory jail term requirements however because a prosecutor could not produce proof of Block's prior conviction and because two of the offenses were considered together. The incidents occurred on May 18 and 19.

Although Block pleaded guilty to one of the charges Aug. 3 and was given a suspended jail term and fine, Assistant Commonwealth's Attorney William Minor Jr. said he failed to bring paperwork about that conviction to Fairfax General District Court yesterday. As a result, he said, Judge John (Gus) Watson refused to consider that conviction in sentencing Block yesterday after he found him guilty of the remaining two charges. Block had pleaded innocent.

Watson sentenced Block to 12 months on each of the two charges, suspended all but one day of the terms, and also suspended $1,000 in fines. On all three convictions, Block's driver's license was suspended for a 5 1/2 years.