Dog control agencies, municipal pounds and pound contractors such as the SPCA, absolutely must - for the safety of the public - MUST kill any dog that they believe to be a threat to human safety. That is why they exist, and to expect a pound not have public safety as its primary mandate is nonsensical. It would leave the pound open to the risk of being the agent of harm, probably to a child.

Until recently, the cheapest way for a pound to do what it must do was to kill anything that seemed the least bit dangerous, and in fact, it became the norm to kill anything that might take up space/money for very long. No municipality gives much money to do dog control.

Thanks to changing public expectations, pounds are now trying to incorporate some animal welfare principles into their duty to protect the public. Change that makes money is fast, change that costs money is slow and so reform of dog control is slow.

The SPCA is in a conflict of interest by being a dog control contractor. To do damage control, after it was exposed on the media for killing nice dogs for space required because of its massive contracting business, but while not giving up the contract money, it devised a "scientific" test to justify killing for space. The test takes the blame off the SPCA by putting it on the dog.

Watch out that pounds aren't forced to go this route by too much criticism of them. Once a test is in place, it is set in stone because it is the perfect screen and business-enabler, and once the dog-disposer can claim that it has science on its side, reform tends to grind to a stop.