Why it took 4 days to release the names of the Toronto van attack victims

After the deadly van attack in north Toronto a week ago today, anxious families and a city in mourning wanted desperately to learn the identities of the 10 people who had beenkilled.

Over the next four days, many peopleexpressed frustration about how long it was taking.Ontario'schief coroner, Dr. DirkHuyer,officiallyreleased their names on Friday,

But unlike the process often portrayed in TV crime dramas, forensic investigators in Ontario go through several steps to scientifically confirm the identity of someone who has died. In fact, the "visual confirmation" step when a family actually sees aloved one'sbody is at the end of the process, when "we're pretty much sure that that's the right person we're bringing them to,"Huyertold CBCNews.

• Learn more about the victims of the Toronto van attack

In the approximately 5,000 death investigations he hashandled duringhis career,Huyersaid, he can't recall an instance in whichsomeone came to look at a loved one's body and said it wasn't the right person.

"That would be one of the most awful things in the world for me to do."

Huyerwas keenly aware of public frustration over the wait for confirmation particularly from the families who believed their loved ones had been killed.Hehad to strike a "balance" between meeting the need for information by the families, the community and investigators, he said, while making absolutely sure his teamgot the identities of the victims right.

"The significance of making a mistake is so large," Huyer said, that even if information points to a "reasonable likelihood" of someone's identity, that's not good enough.

The devastating consequences of misidentifying victims in a mass casualty situationwere made clear earlier this monthwhen one family was led to believe a loved one had survived the Humboldt Broncos bus crash in Saskatchewan, only to find out later that he was one of the16 people who had died.

In the Toronto case, the eight women and two men, ranging in age from 22 to 94, who died were all run down in a seven-minute rampage by the driver of a white rental van tearing down Toronto's busy Yonge Street, mounting sidewalks and veering into the opposite lane. Alek Minassian, 25, has been charged with 10 counts of first-degree murder. He also has been charged with 13 attempted murder charges and is expected to face three more.

Here are the steps that the coroner's office and investigators gothrough to reach a definitive identity confirmation:

1. At the scene

Investigators gettheir "first clue" to start the process of identifying victims at the scene, Huyersaid.Theylookfor identification such as a driver's licence. They may also find people in the area who knew the victims and witnessed the attackwho can confirm details such as what someone who is unaccounted for was wearing when they saw them earlierin the day, their ethnicity, hairstyle, eye colour andother aspects of their appearance.

Other leads come from descriptions and photographs provided byfamilies or friendswho haven't heard from their loved ones and believe they were in the area at the time.

But the names of potential victims that emerge from all that information are only a starting point, Huyer said, and investigators have to be careful to stay "very objective" at that point.

"You can go down a pathway and convince yourself that all of these things match quite well," he said. "But all of those individually are not very strong [identification] features. Because you can change your hairstyle, you can change your hair colour.Eye colour may change with contacts.All of these things you have to be very cautious with."

2. Fingerprints

Fingerprinting is often the first tactic investigators try in order to get a scientifically soundidentity confirmation, Huyer said.This method was successful in identifying "more than one" of the 10 people killed in the van attack.

In New York City, fingerprinting has become one of the main ways victims are identified, ever since the city'smedical examiner's office got rapidaccess to local and federalfingerprint databases acrossthe U.S. in 2012, the office's deputy commissioner, Frank DePaolo, told CBCNews.

Fingerprinting provides identification for 30 to 50 per centof people involved in mass casualty incidents in New York,DePaolosaid.

"They get done very rapidly," he said. "It's really been a game-changer."

DePaolo saidfingerprints are often available because they are taken in many circumstances in the U.S., including when foreign nationals enter the country. They're also taken frompeople who have served in the military, during some licence or job applications, and in the criminal justice system.

But Huyer said fingerprints don't lead toidentifications as often in Canada.

3. Dental records

Dental recordswere used to scientifically confirm the identity of themajority of the 10 people killed in theToronto van attack, Huyersaid.

"There's good, solid, multiple ways to confirm by dental X-ray comparison," he said. That's because people often have unique features in their teeth including dental work.

Once investigators determine who they believe a deceased person is, based on multiple factorsgathered in the initial steps of the process, they contact family members and ask for the name of the person's dentist so they can continue to the scientific confirmation step, Huyer said.

The van attack happened at about 1:30 p.m. ET on Monday, April 23. By about 3 a.m. on Tuesday, they had a "good idea" of who all 10 victims likely were, Huyer said, and they were ready to approach family members and ask for dental information.

"We said to the families, 'We think your loved one just passed. We don't know, we think so, and we need to confirm and to ensure that we have the identification right.'"

4. BodyX-rays and examinations

If investigators can't get dental information sometimes because they can't find the person's dentist, or the person doesn't have their naturalteeth they turn to other identifying factors that may exist inside their body.

Previous X-rays can yield important clues such as past bone fractures, which are still visible when the person is deceased. If someone had arthritis, X-rays can also show extra bone growth on the edges of a vertebrae or a joint, which can also help prove the deceased person is who they believe he or sheis.

If the person they believe was killedhad their appendix or gall bladder removed, the coroner's office cancheck to see whether the deceased person had undergone the same procedure.

A much more definitive confirmation can be made if a victimhad an implanted medical device, such as a pacemaker or knee replacement, because they have serial numbers on them, Huyer said. That means they can compare the serial number on the device inside the deceased person withthe number contained in records of the medical procedure that he or she had undergone.

5. DNA

DNA is generally considered a scientific confirmation, Huyer said, when it matches DNAtaken from a known close relative of the deceased person, such as a child or parent.

Investigators can also gather DNA from personal items used by the person believed to be deceased, such as a razor, toothbrush, hairbrushor comb.

But once again, as with all confirmation methods, investigators need to be meticulous, Huyer said.

"You have to be quite confident that the person who used that razor is in fact that deceased person."

Identifying all 10 deceased victims at once

Withholding official identification ofthe deceased until all 10 had been scientifically confirmed was another way to guard against mistakes, Huyersaid.

"You compare [victim] number oneand you double check it. You compare number two, double check it.And just in case number threeand number fourmight be mistaken in some way because we just didn't do something perfect, we take the whole data set together before we can actually accept that all 10 are correct."

Huyer said he understood how painful it could be for the families to wait for confirmation, and he spoke to loved ones who had concerns to explain the process.

They notified the families Thursday night and Friday morning before releasing the identities to the public, he said.

Even though families may have known since Tuesday that their loved one was likely gone, the final confirmations mean the coroner's office can legally release the bodies andprovide death certificates.

"[The confirmation is] the trigger to allow them to proceed with the next steps, which is planning the funeral, telling other family members, moving on from all of the speculation in the mediaand the publicand in the community, of whether somebody may or may not be dead," Huyer said."Thatwas ended."