def turned_red(metric, most_recent_measurement_seen: str) -> bool:
    """Determine if a metric turned red after the timestamp of the most recent measurement seen."""
    metric_is_red = metric["status"] == "target_not_met"
    recent_measurements = metric.get("recent_measurements")
    return bool(
        metric_is_red and recent_measurements and recent_measurements[-1]["start"] > most_recent_measurement_seen)