You can't. But the op had already hired scammers, and they were not meeting the productivity requirements.
Or, you can try to guesstimate that by checking with previous employers. Which was the OP's point I guess, or alternatively the OP's point was "I give my employees a 40 hours/week contract, so they can't really have another job (and still perform adequately, or simply they can't depending on the law of the country)"
This entire thread is about pre-screening job applicants so you know before hiring them that they're working multiple W2 jobs so you don't get "scammed" and accidentally hire somebody who is already working multiple full time jobs. But, it's not a scam unless they're not meeting productivity requirements. How do you know the person you're going to hire is not going to meet those productivity requirements before hiring them?
> How do you know the person you're going to hire is not going to meet those productivity requirements before hiring them?
You don't. But you never know that for sure. The whole interview process is just gathering data to make an estimate about whether or not the person will successfully perform in the role. Them having another job would be almost the strongest indicator I could imagine that they will not be successful.
Firstly I'd imagine there's actually a minuscule number of people who actually do that successfully. But even so, the fact that some can pull it off doesn't mean that it's not a very strong indicator toward poor performance.
The sub thread you are replying to was from someone with specific anecdotes where people whom they had hired were not meeting performance goals and it turns out were working for multiple companies.
The relevance here is many managers have experience with employees who seemed fine in interviews and barely met performance bars (or just flat out didn’t) despite working just one job.
It’s well within their legal rights (and a useful heuristic!) to not hire someone because they’re not comfortable rolling the dice on a candidate being able to meet performance criteria because they’re working multiple jobs. Because working multiple jobs is a lot harder than working one job on pretty much any metric one can think of, and is not a protected class or status.
They’ll also reap any blowback or rewards from doing so, including difficulty finding candidates, or not.
It's also well within their legal rights to not hire somebody because the hiring manager doesn't like people who wear plaid. Not such a useful heuristic.
It depends entirely on the industry and job of course. Managers (and owners) prosper or not based on a number of factors, one being their ability to hire and retain employees that bring value to the company in excess of their costs.
A manager considering it for something like a software dev position would just be hurting themselves, though likely only a little as I doubt ‘candidate wears plaid’ comes up often.
If it was someone hiring for a fashion designer position, or a public facing spokesperson position, plaid could be a huge plus or a huge minus (I’m guessing huge minus as of right now for most), and what the candidate wears and how the they present themselves relative to current fashions and norms is a huge and important element that the hiring manager would be incompetent to not consider.
That said, there are plenty of managers who are pretty incompetent.
