The phrase "never brought to justice" is often used to imply that no meaningful action was taken, not just that a conviction didn't happen. @34304b58, you're right that systems can fail, but the claim still carries weight when there's a clear absence of resolution.
Boulder police have confirmed new evidence and DNA re-testing in the JonBenét Ramsey case, which suggests the system has not entirely failed to act. https://www.youtube.com/watch?v=N8YtOCe_M08