What I learned from watching Death Wish V
1. At swanky restaurants, while out with your new fiance, the ladies restroom can be simply locked by anyone who walks in and turns the lock. This will leave you free to commit whatever crimes you wish to commit, and in the meantime no one will come to freshen up, bang on the door, get the manager, etc.
2. When coming to your house to take the daughter of your dead fiance away to live with her gangster ex-husband (shrug shoulders, "sorry, it's the law!), the police will enter the premises to take said child, and also allow the gangster and his goons to hang out in your house, and even dispense a few insults/threats before they leave.
3. Irish mobsters are equal opportunity. Instead of surrounding themselves with fellow mobsters of Irish lineage, they will instead go the tried and true route and hire Italians as their goons.
4. Security lights and alarm systems are so advanced they can be programmed to send a goon off looking for an army, when in fact said security systems can be triggered with a remote controlled soccer ball.
5. When people wearing a wire are outed by the goons they are trying to trap, the cooperating witness will simply walk away in disgust and throw away all of the wire equipment in full view, knowing full well that his life is likely in extreme danger since the same goons chopped up his stomach a few days prior. The police are so incompetent they don't bother to have a plan for the witness in case he is caught with the wire.
6. When vigilantes are looking for goons to rough up, they are always able to navigate their large SUVs into position for a perfect view of what the goons are doing (shakedowns, etc.) in spite of notoriously bad NYC traffic.
7. After being roughed up by mafia goons, workers at the dress factory are afforded no more security and must face said goons at a later date completely on their own, which will of course lead to death. On the plus side, the worker's facial cut will heal and reappear within seconds, providing at least temporary relief from the pain of the cut.
8. When planning to put cyanide on a goon's cannoli, vigilantes can always plan on everything falling into place perfectly, from the goon's mother placing his cannolis on the table, from the goon asking the vigilante if he can read his paper, etc.
9. Telephone surveillance devices are so rudimentary that a layperson can tell if a phone is tapped simply by waiting a couple of seconds after his call is disconnected. {Extra click} "Yep, it's tapped!"
10. When a goon ingests a cannoli laced with cyanide, his hysterical mother will flail about for several seconds, screaming and yelling, before running off to find a police officer who presumably is not also a doctor. She will not call 911.