In People ex rel. Dept. of Transportation v. Superior Court (2003) 105 Cal.App.4th 39, a husband and wife were driving on a road that became engulfed in smoke from a fire. They pulled to the shoulder of the road. The husband escaped the car with burns, but his wife was killed when the car caught fire. The husband was hospitalized and emotionally upset after the incident. He learned from newspaper accounts that the fire was started by an arsonist. (Id. at p. 42.) He did not seek legal counsel until approximately seven months after the incident, when his barber suggested he speak to another customer who was an attorney. Eight months after the fire, the husband and his two sons filed claims against Caltrans, which were denied. (Id. at p. 43.) The trial court granted relief from the failure to make a timely claim against Caltrans based on mistake, inadvertence, surprise, or excusable neglect, but the Isenhower court reversed. It noted that excusable neglect to justify relief from the claim-filing requirement is not shown by the mere failure to discover the potential of governmental liability until it is too late. Rather, a plaintiff must show reasonable diligence to discover it. (Isenhower, supra, 105 Cal.App.4th at pp. 44-45.) While the husband believed that an arsonist had started the fire, that belief did not excuse his failure to retain counsel or investigate the potential responsibility of Caltrans for six months after the incident. (Id. at p. 45.) Nor were the husband's injuries or emotional distress an excuse. His claimed emotional distress was self-diagnosed, and there was no evidence it or his injuries interfered with his ability to seek out legal counsel. (Id. at p. 46.) Indeed, such conditions could be attributed to every accident victim. (Ibid.) Were they debilitating enough to excuse the claim-filing requirement, they would have risen to the level of incapacity, identified by section 946.6 as a separate ground for excusing timely claim filing, but there was no evidence that was the case. (Id. at p. 46; see 946.6, subd. (a)(4).)