In fact, I have been contacted as much as two years after the incident. It is critical to evaluate the dog as soon after the incident as possible because an expert opinion based only on hearsay or deposition testimony is not nearly as powerful as one that is based on actually seeing and testing the dog in similar circumstances. This is equally important for both the plaintiff and the defense. The lawyer should try to get permission to evaluate the dog before it is either euthanized or given away to some stranger, never to be seen again. Talk to all the neighbors.
Neighbors always know a lot about the typical behavior of the dogs on their block.
They may pet them as they pass by, or they may avoid them because they see them as potentially dangerous. Neighbors also know if the dog ever gets out of the yard or if the owner allows the dog to wander the streets. And they are good sources of information about prior incidents. Interview the dog's veterinarian. The veterinarian is a good source of information on how the dog acted prior to the incident.