Your dog bit three people. Drew blood each time and now you’re told, “It’s time to euthanize, time to put the dog down.” To the non-dog person the third bite is two bites too late. But what does the dog owner hear? “You’re telling me to kill my dog. Kill a family member that I love dearly?”

It’s one of life’s gut-wrenching decisions. I’ve been lucky. Of the six family dogs in my life I have never been faced with the need to euthanize because of aggression. But I did have to make the decision based on old age and quality of life issues, a time to go home, as Jon Katz writes in his book, Going Home.

But what about when the dog bites? There are several veterinarians in New York city who used to routinely call me every time the question came up. Making that decision was part of my job, and by far the hardest part. As a dog trainer, half of my over 800-job case load comes down to dealing with behavioral issues and aggression is high on the list. I’ve had numerous sleepless nights knowing that in the morning I will have to tell a family to kill their dog. But that doesn’t always have to be the end result.

When someone comes to me and says, “My dog bit someone, do I have to put it down?” my answer is, it depends. I recognize at least six different types of aggression, so I need to meet the dog and see for myself. For example, the dog that bites out of pain aggression would never have to be put down. Your dog gets hit by a car, has a broken leg and bites you because of the pain of being moved is certainly not a case for euthanasia. I’m also not going to use the same methodology for a new 12-week-old toy poodle as I’m going to use for a three-year-old German Shepherd that bit two people.

People have often asked, “Are there dogs that just can’t be trained?” My answer to this is aren’t there people who are in institutions because they can’t make it in society? Unfortunately, for dogs that can’t be integrated with us there aren’t any institutions.

But in this same respect, a loving, smart, cuddly, cooperative dog that will bite all non-family members does not necessarily have to be euthanized. It’s a management situation, making sure the dog doesn’t get the opportunity to bite a friend or stranger. It’s also a much larger liability if the potential biter is a Great Dane as opposed to a Chihuahua.

But this strategy is not without risk. When the doorbell rings, saying “I’ll be right there, just let me put the dog away,” is subject to human error. The dog is put in the bedroom, but accidentally the door didn’t latch securely.

I do draw the line at serious aggression directed at family members. I have walked into houses where the fear of the dog is palpable. I’m not talking about the dog growling at the food bowl, or a warning snap, either. This is when the dog, for whatever reason, attacks with an unrestricted bite. Dogs learn bite restriction in the litter. When the puppy bites the mother too hard, the mother straightens him out, or when a pup bites a litter mate too hard causing it to cry, the biter learns to restrict the force of the bite. This is one of the reasons pups shouldn’t be removed from the litter too early. Working police dogs often have to have their bite “unrestricted” as part of their training.

I try to work with a dog on their unrestricted biting but if I can’t turn the relationship around and make the family, the whole family, safe with the dog, the dog gets euthanized.

So how does one actually kill a family member? When asked how to actually go about it, this is what I’ve told my tearful clients. Dogs are extremely aware of your emotional state. Do not freak them out with your sadness. Act happy and if possible have the vet come to your house. Give your pet a great treat as he gets the shot. My dog Tri died with his tail wagging furiously while eating a Nestle’s chocolate bar. Then mourn till you can’t anymore.

Tom Shelby began his career as a professional dog trainer in 1972. In addition to working with private clients, Mr Shelby has consulted for the K-9 search and rescue unit of Rockland County, N.Y. Currently, Mr. Shelby lives on Martha’s Vineyard. For more information about his work, visit dogsrshelby.com.