A case over car tabs in Washington went before the state Supreme Court Tuesday, highlighted by an admission from Sound Transit that it had been using the wrong depreciation schedule to levy taxes.

The case against Sound Transit alleges that the voter-approved ST3 transportation funding package was worded in a way that violates the state Constitution.

Joel Ard, the lawyer for the taxpayers, says that officials are not allowed to enact the change they way it did. It literally has to spell out the law its changing; voters have to know what the change is.

“Our constitution requires that they set the forth the amendment in full length, and they didn’t to that,” Ard said.

Supreme Court ready for ST3 car tab battle Tuesday

Ard’s case may have gotten even stronger Tuesday, after Sound Transit admitted it had inadvertently used a 1998 depreciation schedule to calculate car tab taxes, instead of the 1996 schedule laid out in ST3 legislation.

“What we had was a stunning admission from Sound Transit,” State Sen. Steve O’Ban told KIRO Radio’s Candy, Mike and Todd Show. “They made a mistake; they were confused. That pretty much tells you that (Sound Transit) violated the Constitution that requires laws be drafted in such a way that’s not confusing to taxpayers and lawmakers.”

Should the state Supreme Court ultimately agree with O’Ban and Ard, it could have cascading consequences for many crucial Sound Transit projects, forcing it to pay back hundreds of millions of dollars collected from car tab taxes since ST3 was first implemented.

Even with those projects threatened, though, that might not be a consideration for the court.

Washington driver caught using black marker to conceal expired car tabs

“[Washington State Justice Steven Gonzalez] said it shouldn’t matter whether this will cost Sound Transit $1, or millions of dollars — the constitution is what the constitution is. You have to comply with it,” O’Ban described.

In the event taxpayers win their case against Sound Transit, it would then head back to a lower court to figure out how refunds for car tabs would work.