I used to work for a company that installed equipment in police cars. I was working with another guy putting the cage in behind the driver's seat. We were both sitting in the back seat adjusting bracket on each side. I closed my door to check the fit and I heard him close his. I looked at him and asked, "How are we going to get out?". Rear cop car doors don't open from the inside.
Luckily he was a little skinny guy and could fit (barely) through the little sliding window. We would've been there a couple of hours if he didn't fit.