Cat Lover’s Site

Aside from the obvious answer of keeping the cats inside?

Has a necropsy ever been done on any of the deceased cats? Do you know what they died of? If you can prove they were murdered, perhaps a call to the police and/or humane society, try to get an investigation going. Unless you can film every moment of their lives (which is pretty much impossible), there is no actualy way to pinpoint something like this, unless you can catch said neighbor in the act.

Sorry for all that you and your neighbors have been going through.

My opinion is that this would not happen if the cats were indoors where they are kept safe. Would you just let a dog wander around without thinking anything could happen to it? The same goes for a cat.

I agree with the previous two answerers.
#1 It would be very difficult to prove or find out at all how the cats are being poisoned or by whom.
#2 It would be easier to keep tabs on your tabbies by building an outdoor run for them or when you are out with them having them harnessed. Many cities have by-laws where cats are to be licensed and not allowed to run free.
We have had many cats over the years and learned to harness them from wee kitties. They get used to it. They are only allowed outdoors when we are working in the garden and such.