I use several methods to slow down thieves. My next door neighbors grandidiots got into one of my greenhouses the year we built it. Got away with enough to trim out to five pounds. After viewing the evidence(dfead leaves in a path to their garage back door, which I could see from my yard,), I confronted the homeowner. She denied the theft. I informed her that I would kill any future thieves. I then installed several measures to deter theft. The following year, they tried, and discovered I had made stealth impossible. They called the police. Pretty soon we had a swat team around our home.(I was at work during the day, so my wife had to deal with half our police department.) She showed them our recommendations, and then gave them a tour of our grow. They approved my design and security measures and haven't returned. A year later, a picture they took of my nearly mature garden ended up on the cover of the city magazine. They were also interested in what we told them about our neighbor. They went over after, and suggested, for their own liberty to leave us alone.
My measures? Chain link topped with barbed wire around the greenhouse walls. The cage is a 16x8 foot chain link dog kennel. Covered with 6"x6" remesh. About August first I string lengths of barbed wire throughout the garden at various heights and angles, making it very difficult to even get to any of the grow areas. I have motion detectors throughout the garden, and keep the base unit on my desk. I NEVER leave home at night from September 1st until I've completed harvest in mid October. All my neighbors(except the one mentioned above) are retired LEOs. They're good neighbors and fully aware of what I do. I've considered buying cameras, but my wife is disabled so our house is almost never unoccupied. Everything is locked up when I'm not actually working in the garden.
I figure some idiot will give it another try, sooner or later. I have several items scattered around the yard in case the thief tries to confront me. The pitchfork stands next to my back door. An old axe, a couple old aluminum bats, and various other implements are hidden around the garden in unlikely spots. I also have a promise from the police that anyone caught in my garden WILL be prosecuted.
Hopefully this will give others a few ideas.