Newly elected and returning Liberal MPs are anxiously awaiting the phone call that tells them they have been chosen to join Justin Trudeau's new cabinet.

But before that happens, extensive background and security checks will have been done on each, in many cases without their knowledge, looking for any liabilities or past indiscretions that would pose a security concern, an embarrassment for the government or make them vulnerable to coercion.

It all starts with a list of names, a list longer than who will actually end up in cabinet. That list is passed from the prime minister-designate's office to the Privy Council Office, which gives it to the RCMP.

Prime Minister Stephen Harper sits with Gov. Gen. David Johnston, front row centre, and members of his federal cabinet following their swearing-in ceremony at Rideau Hall in May 2011. Prime minister-designate Justin Trudeau's cabinet will be sworn in Nov. 4. (Chris Wattie/Reuters)

William Elliott, RCMP commissioner from 2007 to 2011, said the RCMP takes the lead on the security and background check, working with the Canadian Security Intelligence Service, local police agencies and Canada Border Services Agency. The RCMP presents its findings to the Privy Council Office, which passes them on to the prime minister-designate.

Some mistakes are big and some mistakes are small. Not everybody knows everything about everybody else. - Former RCMP commissioner William Elliott

"It may or may not be information that would impact on a decision on whether to appoint someone to cabinet," he told CBC News. "The vast majority of the times.... we found no adverse information."

But Elliott, who prior to being RCMP commissioner served as prime minister Paul Martin's national security adviser, said there is sometimes surprising information uncovered about candidates.

"When you've held some of the jobs that I have had … you kind of tell yourself nothing should surprise you, but I think we have all made mistakes, and some mistakes are big and some mistakes are small," he said. "Not everybody knows everything about everybody else."

Elliott said the RCMP, CSIS and other agencies check their databases for red flags, including:

Criminal records.

Outstanding warrants.

Outstanding investigations.

Any police contact with the person in question.

There are more databases accessible to police than ever before, from child pornography and sex offender registries to DNA data and fingerprints, Elliott said. Even if a person was witness to a report of criminal activity, that might be revealed.

And, unlike a decade ago, the RCMP also conduct searches of social media.

But there could be unresolved questions if red flags come up and there isn't time to delve into those alerts in the short period between the end of an election and the selection of a new cabinet.

"There might be an indication that more information would be desirable and the incoming prime minister would have some options," said Elliott. "He could decide it is not important enough to affect his decision or he could decline to appoint the person."

The interview

Senior bureaucrats who have been involved in the process in the past told CBC News there is a second part to the vetting process after the RCMP's security check: an informal interview with a senior bureaucrat or member of the prime minister-designate's team.

Trudeau says he will have a smaller cabinet than Harper's. His cabinet will be sworn in next Wednesday. (Adrian Wyld/Canadian Press)

That's where the question, "Is there something you know that we don't know," would be asked, said one former senior bureaucrat on condition of anonymity.

That could be a secret that would make the person vulnerable to bribery, extortion or some type of coercion, or it could be a conflict of interest that needs to be sorted out.

When it comes to conflicts of interest, that's where Ethics Commissioner Mary Dawson comes in.

"We are very open to those conversations," said Dawson. "If one of those individuals who is being appointed wishes to speak with me, I will."

And once new ministers are actually sworn in, Dawson immediately sends them all a letter asking for detailed information about their assets, their holdings, their outside activities and the dealings of their family and friends.

Secrets are hard to keep

Former Liberal cabinet minister Lloyd Axworthy said that by the time someone is being considered for cabinet, they've already passed at least a basic vet, and if something embarrassing was going to come up, it likely would have during the campaign.

In this latest election, a record number of candidates from all parties either bowed out or were dropped over past comments made online or actions that were caught on camera.

"It's very hard in this day and age to keep anything in the closet," said Axworthy.

Former Conservative minister Stockwell Day said even past bankruptcies and litigation are of interest. But, he said, by the time a prime minister calls to deliver the good news to a minister-to-be, all the questions have been asked and answered to the prime minister's satisfaction — so there isn't the risk of an awkward call the next day.

"It's rare that something would come up after the fact. But there is always a chance of a surprise," he said.

Of course, such checks are not predictive of future behaviour. In response to a security breach by former foreign affairs minister Maxime Bernier in 2008, Prime Minister Stephen Harper ordered security clearances be done every two years.

Elliott said it's unlikely one thing would rule someone in or out of cabinet.

"What's relevant is, is the person trustworthy, is there any reason to worry about whether the individual could carry out their responsibilities appropriately and keep the secrets, the confidences that they will be privy to."