"Time is not on the side of the investigators" in the Tess Richey murder case, says one former homicide detective, with days of work having been lost and a crime scene potentially compromised by what had at first been a missing persons probe.

Richey, 22, went missing in the early morning hours of Nov. 25, and was found dead on Nov. 29. Over the weekend, police released surveillance photographs of a man they'd like to speak to who was seen with Richey shortly before her death.

Last week, Mark Mendelson, a former homicide detective with Toronto police who currently works as a private investigator and consultant, said anytime a missing person investigation turns into a murder probe, it "creates more work" for police and forces them to retrace their steps.

Witnesses must be re-interviewed, video from security cameras must be collected and viewed, and information from the victim's cellphone will have to be analyzed.

"These are all steps that would normally be taken during the course of a homicide investigation, not necessarily at the front end of a missing person investigation," Mendelson told CBC Toronto.

"It just creates more work."

Richey's family notified police of her disappearance after not hearing from her all day following a night out with a high school friend. They drummed up public awareness and organized searches in the Church and Wellesley area where she was last seen. Her family says her mother found her body just steps from where her friend last saw her.

The family has been critical of how police handled the investigation in its early days. Last week, the Toronto police professional standards unit launched an investigation into how officers approached Richey's disappearance. On Friday, Chief Mark Saunders said the probe is a chance for the force to review and analyze its procedures in missing person cases.

'A number of questions that need to be asked'

Mendelson could not speak to the specifics of the investigation into Richey's disappearance. However, asked about the typical process that police follow when starting a missing person investigation, he said detective shows on television have created a bit of a misconception.

"Well, the whole theory of 24 hours before anything can be done is really something that you do see on TV and it's not a hard-and-fast rule in any police service, certainly in North America," Mendelson said.

"It all involves the circumstances surrounding the disappearance, and there are a number of questions that need to be asked and answered in order to determine the priority that it's going to receive."

These questions include:

Has the person gone missing before?

Is such behaviour out of character?

Is the person dealing with mental health issues?

Does the person take medication that they don't have in their possession?

Is the person engaged in a high-risk lifestyle?

Did something precipitate the person going missing, such as an argument or domestic incident?

"There are a whole bunch of factors that need to be taken into consideration when one decides how involved in the initial stages the police are going to be," Mendelson said.

In all cases, information about the missing person, including their name and date of birth, is put out to the Canadian Police Information Centre (CPIC) so all police services are aware of the disappearance.

After that, investigators have to "make some assessments" to determine the next steps, including figuring out who was last in contact with the person and what their last plans were. Police then check into factors such as whether they have used their debit card in the time since they went missing.

Whether uniformed officers get involved in a physical search depends on whether police suspect foul play, Mendelson said.

"It's a big step, especially with an adult, to get into that physical search of neighbourhoods or buildings," he said.

'Difficult to backtrack'

Mendelson said no when asked whether a probe starting as a missing person investigation compromises what ultimately becomes a murder investigation. But he did say it "certainly creates more work" for homicide detectives.

"As a homicide investigator it's a little difficult to backtrack, to go from a missing person to a found missing person who happens to be deceased," he said.

"Because your crime scene has been tainted in many ways, and obviously it takes on a whole higher level of investigative practice because it is a homicide."

The key now, he said, is to catch up with the man who was caught on surveillance footage with Richey before she died.

"He's absolutely a person of interest," Mendelson said. "And now they have to find him."