Legal Question in Real Estate Law in California

It should be legal. Check with your local building department to see how high a fence is allowed. If you had a two story house you could look over your neighbor's fence so merely looking would not be against the law. As you are trying to spot a criminal activity there is nothing against taht anyone would complain about. If your neighbor is mistreating their dog who is going to listen to any of their complaints. I assume the dog is crying so you basically are trying to render aid.

Generally it is perfectly legal to look at your neighbor's house and to photograph it. Technically, you would be trespassing if you put your fingers, or the nose of the camera, across the plane of the property boundary, but even then investigating an emergency or a possible crime may be a defense. Further, the damages for a nominal trespass with no harm done is probably about $1.

I should probably add that while looking over the fence and taking pictures are generally legal, matters can be pushed to the point where there may be some ground for the neighbor to sue, such as if matters rise to the point of civil harassment, or the picture-taking is accompanied or followed by an improper invasion of privacy. Also, the law frowns on "peeping Toms" who intrude on sunbathing, dressing, bathing, etc.