A long-running age discrimination suit against 3M Co. is back in Ramsey County District Court, and an attorney is once again seeking to turn it into a class action on behalf of as many as 5,000 3M employees.

The suit was originally filed in 2004 on behalf of six 3M employees who alleged they were discriminated against based on age during the tenure of CEO James McNerney Jr., which extended from 2001 to 2005.

After hearing arguments over class-action certification -- in which plaintiffs and 3M attorneys presented anecdotal and statistical evidence to refute the other's positions -- District Judge Gregg Johnson took the case under advisement. By law, he must rule on the case within 90 days.

The suit, which has had an up-and-down history, was previously certified as a class action by Johnson in 2008, but last year the Minnesota Court of Appeals returned the case to the lower court with instructions to review whether the "preponderance of the evidence" justified making the case a class action.