Lawyers for the family of a Nova Scotia teenager who died 27 years ago say there is a major development in the case.

Ray Wagner said his firm will announce the findings in the Clayton Miller case at a news conference on Monday in Halifax.

Two investigations — conducted by Nova Scotia's chief medical examiner and the province's independent police watchdog — concluded in 2015 that the 17-year-old was drunk when he fell into a stream in New Waterford while trying to run from police, who had raided a nearby bush party on May 4, 1990.

Doctors had come to differing conclusions about the cause of his death and a subsequent inquest and RCMP investigation both cleared the New Waterford police department of any wrongdoing.

But over the years, Miller's family has raised questions about the circumstances surrounding the teen's death, saying they believe key information was withheld from the public.

They have long called for the investigation to be reopened.

In a news release, Wagner said the firm is determined to "expose the truth of what happened to Clayton."