Reviewed and updated October 9, 2026 by the SearchSystems.net editorial team. The arrest counts are the ones each agency reported to the FBI, as the FBI held them on October 8, 2026. The jail figures are from the Vera Institute of Justice's Incarceration Trends data. Every office link was opened and checked against the office's own site between September 23, 2026 and September 25, 2026.
Mercer Island, Washington, in King County, has about 25,000 residents (2024 Census Bureau estimate). A DUI arrest in Mercer Island starts two cases, a criminal case in the District Court or a municipal court and a license case before the Department of Licensing, and leaves three records. This guide follows the arrest from the roadside to the court file and the driving record.
This guide covers the law, the arrest, booking, the court case, the license case, the records and common questions.
Related guides: Mercer Island public records, King County DUI, Mercer Island arrest records, Mercer Island warrants, Mercer Island inmate search, Mercer Island criminal records, Washington arrest records and Washington inmate search.
The DUI Law in Washington
Drunk driving is charged as DUI in Washington, at a blood alcohol level of 0.08 or more.
Driving in Washington is consent to a breath or blood test when an officer has cause to suspect DUI; the license case that follows a refusal or a failed test is run by the Department of Licensing, separately from the criminal case.
For charging and sentencing, Washington counts prior offenses within 7 years.
Who Makes DUI Arrests in Mercer Island
The King County Sheriff's Office and the agency that reports for Mercer Island (filed by the FBI as Mercer Island Police Department) make the DUI arrests in and around Mercer Island.
The FBI's agency list also places these agencies in King County: the University of Washington (campus police); the Port of Seattle (other agency).
Together, the 36 agencies in King County with all twelve months of 2025 on file reported 31,397 arrests to the FBI that year, all offenses together; the FBI's count for King County does not break DUI out.
The Milton Police Department is listed by the FBI across two counties including King County, so its arrests are not broken out for King County here.
Booking After a DUI Arrest in Mercer Island
A driver arrested for DUI and kept in custody goes to the county jail, whichever agency made the arrest. The jail, run by the King County Sheriff's Office, held about 1,330 people on an average day in 2024 by the Vera Institute of Justice's count and has a jail page SearchSystems verified at data.kingcounty.gov/Jail/Names-dates-charges/yri2-fef8, phone (206) 296-1234. The Mercer Island inmate search guide covers the jail in full.
The Court Case
A DUI charge from Mercer Island is heard in the District Court or a municipal court; the Prosecuting Attorney or, in a municipal court, the city's own prosecutor brings it.
The Prosecuting Attorney's page SearchSystems verified is at kingcounty.gov/en/dept/pao, phone 206-477-1200.
The court records page SearchSystems verified for the county is at kingcounty.gov/en/dept/dja/courts-jails-legal-system/case-records/r..., phone 206-477-0691.
Statewide, Washington Courts Search Case Records is the Administrative Office of the Courts' free statewide case search.
The License Case
A DUI arrest starts two cases: the criminal one above and an administrative one over the license, run by the Department of Licensing. The driving record, kept by the Washington State Department of Licensing, carries the result of both.
The Records a DUI Leaves
- The arrest report: from the agency that made the arrest, under the Public Records Act (RCW 42.56).
- The court file: from the District Court or a municipal court, kept by the County Clerk.
- The driving record: from the Washington State Department of Licensing.
More on each: Mercer Island arrest records, Mercer Island police reports and Mercer Island court records.
Frequently Asked Questions
What is the DUI limit in Washington?
0.08 percent blood alcohol.
Where is a DUI case from Mercer Island heard?
In the District Court or a municipal court. The court records page SearchSystems verified for the county is at kingcounty.gov.
Where is a person arrested for DUI in Mercer Island held?
At the county jail, run by the King County Sheriff's Office, if kept in custody.
Who handles the license after a DUI arrest in Washington?
The Department of Licensing, in an administrative case separate from the court case.
How long does a DUI count as a prior in Washington?
7 years.
Is this the official Mercer Island website?
No. SearchSystems.net is an independent public records guide, online since 1997. It links to the official city, county, court and state offices described above and does not hold records, charge for them or take requests.