A recent ruling by the California Court of Appeal said that plaintiffs alleging age discrimination on the part of an employer can use evidence from co-workers to back up their claim, known as "me too" evidence.
The court said that the co-worker evidence cannot alone prove an employee was discriminated against because of age, but it can be used to show a pattern of age discrimination by the employer or to help prove that an employer's given reason for firing an employee was actually dishonest and a front for age discrimination. For a co-worker's evidence to help back up a plaintiff's claim, it is also important that they have similar situations.
To prove that an adverse action taken against them by an employer was due to age discrimination, an employee must prove that they were at least 40 years old when it occurred, that they were competent at their position, that they experienced an adverse action and that circumstances suggest age discrimination was a motive for the adverse action.
In making their decision, the California Court of Appeal looked to the federal Age Discrimination in Employment Act. Under federal law, "me too" evidence can be used by plaintiffs to show a pattern of discrimination. The court decided that "me too" evidence could be relevant under the California Fair Employment and Housing Act (FEHA).
Age Discrimination: Plaintiffs Can Use Evidence of Bias Against Co-Workers (HR.BLR.com)