Should I wait for the background check to clear before leaving current employer when I know my background is clean

Danger.

It could be hours, days, weeks or months before the background checks are done.

The average time for your new employer is immaterial. I have known situations where the HR person went on vacation so everything stopped for 2 weeks. I know of a family member who submitted everything, took the drug test, got the results but the company never started the criminal check. That delayed the start date by a month.

Until all the conditions have been met, the offer can still be rescinded. That means you could be unemployed. I knew somebody this year who had their new company ghost them in the final stages.

I have received and accepted an offer, I have an orientation date and the training department has called me.

Orientation and training dates will be shifted until a non-conditional offer has been issued and the start date has been negotiated.

I know of a company who only started people every other Monday. Miss the cutoff and that will delay everything by two weeks.

The risk is that you tell your current employer you are leaving and then you are unemployed while nervously waiting.

Don't tell your current employer, until you have to. Keep applying and interviewing until you start the new job.

Yes, you should wait.

Because every week that the background checks take is another week in which your new employer can change their mind for reasons unrelated to the background checks..

Your new employer may be hit with a lawsuit, or be bought out, or just have an internal reorganization. Any of those could result in your not-yet-final offer being withdrawn.

The other question is: have you been given a start date? If not then what day are you going to give for your last day at your old employer? If the criminal background check drags on for months (yes, I have had that happen to me!) and you gave two weeks notice how are you going to pay your bills for those months? If they have given you a start date then you are probably OK quitting soon enough to allow you to start on that date.

The conventional wisdom is don't hand your notice in until all paperwork for the new role is done and everything is all but certain.

However, I've had (independent contractor) roles in the past where the background checks were still "pending" about 2 months after I'd started actively working at the client site due to what were ultimately communication problems inside the background check agency that took a lot of to-ing and fro-ing to iron out.

If it's just your criminal record checks left, and you're confident you don't have a criminal record then it's a much lower risk than if they'd not made the offer at all and you'd not accepted it or passed all other initial checks.

You've presumably got details of a HR contact (or the hiring manager) by now - it might be worth talking to them about how you should proceed. They hopefully understand your (quite reasonable) caution and might say it's not a problem to wait until all your checks are passed, in which case there's no drama and you can just do that.

And if they start making a scene about the delay, you've had an advanced warning about the culture there and you can consider if you still want to accept the offer :-).

Most importantly, arrest is not something what would harm you. Arrest means that there is enough suspection for that you committed some serious criminal offense. If you are not convicted, then you are clean like the fresh snow.

Second, the company is not an investigating authority. They are not even permitted for that. Criminal background check means that they ask you to show your clearance.

What are they doing, well that is really interesting question. Most likely, they ask for papers from some authorities.

In my experience, such "background checks" are mostly formalities. Your real background checks happened as a boss/HR has googled and searched for you in all the existing social media accounts. Sometimes the company needs this for you in order to send you to some (mostly, government-related) projects. And that was it.

But the most important thing: you clearly show you do not even have a first workday date. That is not an offer. If you do not have an offer, you have nothing to accept or reject. You can safely and very politely talk to the new employer, you are waiting their offer because you would happily work with them. And you say nothing to your current employer. You will decide if the offer is there.

You should not even stop to resign. You should not even stop or cancel your other, current application processes. They expressed their wish to employ you, that is a happy day, but not a reason to change anything, particularly nothing irrecoverable.