> How do you estimate the weight of a person?

Practice. In theory if you're doing this a lot, you should be able do a decent job of estimating +/- 10%, which is more than accurate enough.

There are certainly other complications (some medications are dosed on "ideal body weight" (ignoring subcutaneous fat), etc...)

I'll second this. Climbers tend to get at least half-way decent estimating the weight of other climbers because it's pretty relevant if you're lead belaying somebody.

In fairness, we're usually estimating the weight of people of fairly fit builds, but with some practice estimating people of other builds, I agree that you'd get within 10%.

A very large part of police work is providing and reacting to descriptions of suspects. If there is no training on this provided then this seems to be a very large oversight. Based on the fact that police constantly arrest and harrass people who 'matched the description' perhaps there is no training, or perhaps the officers simply don't care and are just looking for a person that fits their bias.

One more reason to leave drugs to qualified personell.

Height + bellysize + muscle size?

Right... how do I get a number from looking at those?

Compare those values to your own weight, and pay attention when you hear someone’s weight to see if it matches your heuristic.

> pay attention when you hear someone’s weight to see if it matches your heuristic

I don't think I've ever heard an adult male ever mention their own weight in public. You can see why it'd be hard to estimate when you don't have any data.

You’ll have to get a job at a county fair running the weight guessing attraction to get enough data. There’s no other way to do it, it’s how we all figured out how to estimate the weight of a human. I’ll call my friend Chucky, he’ll get you a gig in a traveling carnival for the summer.

Or simply any job that requires checking IDs. Bouncer, bartender, cashier in a store that sells alcohol/cigarettes, etc.

Huh, I have never seen weight specified on any ID.

Every US ID and driver's license I've ever seen (and I've seen many) list height and weight.

Watch a fair amount of boxing and practice that way.