Determining "adoptability" is one of the greatest challenges in the world of animal rescue. 

"No Kill", or "limited admission" organizations attempt to solve the problem by refusing to take animals into their care who may not be easily adopted to the public at large. The organization has every right to structure itself this way, but too many groups use "no kill" as a way to belittle other groups who may make a different decision about adoptability. The general public hears "no kill" and thinks such an organization is better than others (as if people who work in animal rescue like to euthanize animals and look for every opportunity to do so). If you study the philosophy behind this term, you will learn that even the originator of the concept believes not all animals are adoptable. His main goal was to eliminate euthanasia in shelters due to overcrowding. In our part of the country we have been successful in doing this.

"Open admission" shelters take every animal that comes to them, but then applies previously determined standards of adoptability before allowing an animal to be released for adoption. If animals are not adoptable by their standards, they may be offered to rescue groups, or they may be humanely euthanized. Just as the limited admission shelters have every right to limit the animals they take in, open admission shelters have every right to determine what happens to the animals in their care. 

If rescue groups take animals from other organizations who have deemed them "unadoptable", it is incumbent on the intake group to determine why the animal is considered not adoptable, and also to judge whether the animal is considered adoptable by their own standards. Usually groups rescuing from other organizations are those with more resources to direct toward medical conditions that open door shelters simply can't afford to treat, or, as in the case of placing animals from overwhelmed shelters, more exposure to adoptive homes. 

Standards of adoptability are often unwritten. It can be very uncomfortable for staff and volunteers to see reasons that animals may not be considered adoptable in black and white. Many people prefer to fall back on the fallacy of treating each animal as an individual case. But professionals educated in dealing with behavioral issues in animals can make accurate (not infallible) predictions about an animal's future, just as veterinarians can make accurate (not infallible) predictions about an animal's future once it's diagnosied with heartworm disease (as an example). 

The Asilomar Accords were an attempt in 2004 by a group of animal welfare professionals to standardize classifications of animals in shelters and rescue groups in order to try to understand how animals move through shelters and rescues. Although these standards are used in many animal welfare tracking software systems, they were just a first attempt, and they fall short in many ways.

But one aspect of the Accords that I believe they got right was to consider unhealthy and untreatable (i.e. unadoptable) those animals that "...have a behavioral or temperamental characteristic that poses a health or safety risk or otherwise makes the animal unsuitable for placement as a pet, and are not likely to become “healthy” or “treatable” even if provided the care typically provided to pets by reasonable and caring pet owners/guardians."

Animals that pose a safety risk that continue to pose such a risk should not be considered adoptable. Note that having bitten is not a requirement here. Possessing a characteristic that poses a safety risk is sufficient. If a behavior professional determines that such a risk exists, that is sufficient. 

We can discuss for hours what exactly the phrase "care typically given by reasonable and caring pet owners"means. Are training classes part of this? Going to a veterinary behaviorist? Using medication? Carefully arranging the environment for the animal's entire life so it is never triggered to become aggressive? But the point here is that people who are adopting from shelters and rescues are looking for pets. They are not looking for projects. 

I have an uncommon view of this situation because of my years of experience both in assessing animals in shelters and rescues, and also counseling owners post-adoption. Each of my passions informs the other. I see the fallout from placing questionable dogs in homes. And I know from my behavior clients that owning a dog whose aggression is easily triggered by normal, everyday circumstances is like living with an abuser. 

As hard as this can be to accept, look at life from such a dog's perspective. Imagine being so fearful of a stranger stretching out a hand for you to sniff that your response is to bite that hand. Imagine being so afraid of visitors in your home that you charge and bite them for the crime of standing up from a chair. Imagine barking endlessly at every sound or sight you've never experienced before because it frightens you. 

There are worse things for a dog than humane euthanasia. 

And it's not as if we don't have plenty of dogs who are looking for homes.

I'd like to finish by quoting Sara Reusche, owner of Paws Abilites dog training and one of the most compassionate and effective dog trainers I know. Sara wrote in her blog:  "We advise against placing dogs who we would absolutely work with if they were already in stable, loving homes, because the sad fact is that they aren’t, and that there are hundreds of lovely dogs with no behavioral issues who could use those resources out there who need help."