Toronto Police have upgraded the charge against Kalen Schlatter to first-degree murder in the death of Tess Richey after finding new evidence.

Richey, 22, was reported missing in November 2017. Richey's mother discovered her body four days later at the bottom of a stairwell at 582 Church St.

A post-mortem examination determined she died of neck compression, according to police investigators. Police initially described the incident as a crime of opportunity.

The 21-year-old Toronto man was arrested in early February and initially charged with second-degree murder in Richey's death.

"New evidence presented itself to us," said Det. Ted Lioumanis to reporters on the courthouse steps, saying an upgraded first-degree murder charge is now warranted.

'Best news we could hope for in this situation'

"I'm not going to get into what the new evidence is (but) I'm going to tell you that new evidence presented itself to us," said following a brief court appearance at which Schlatter's case was put over until April 23.

Tess Richey, 22, went missing on Nov. 25 after a night out with a high school friend. Her mother found her body four days later. (Tess Richey/Facebook) There are a handful of conditions under Canada's Criminal Code that can result in a charge of first-degree murder. "Planned and deliberate" homicides and killings that occur while committing or attempting a sexual assault or kidnapping are among the crimes that qualify.

"It's quite typical to see charges upgraded or downgraded as the case proceeds through the court system depending on what new evidence comes forward," Toronto lawyer Daniel Brown told CBC Toronto.

"The police must have evidence either that the case was planned in advance or that it occurred in the course of another crime, such as sexual assault or forcible confinement."

Police believe Schlatter and Richey did not know each other before the night of her death, Lioumanis said outside court, adding that Schlatter has not yet provided investigators with a statement.

"This is the best news we could hope for in this situation," said Richey's mother Christine Hermeston and sister Rachel Richey in a statement sent to CBC Toronto.

They also said they will "continue to honour and remember Tess and the joy and love she brought to so many lives."

Schlatter appeared in court by video, dressed in an orange jumpsuit, his hair neatly combed and his beard trimmed close. He spoke only to say "good morning" and provide his name at the start of proceedings.

Police faced public criticism for their failure to find Richey in the days after her disappearance.

Her death, along with several other disappearances connected to the gay village, led community members to say police were not protecting them.