A California court will determine whether a defamation suit filed by Crystal Castles songwriter Ethan Kath will proceed against the Toronto duo's former singer, who publicly claimed he sexually abused her for years.

Kath seeks unspecified damages in documents filed in a Los Angeles Superior Court under his birth name Claudio Palmieri.

The document alleges that online accusations made by Alice Glass, whose real name is Margaret Osborn, destroyed Kath's reputation and caused the cancellation of a North American tour worth more than US$300,000.

The case targets Glass and other unidentified parties in complaints including defamation, conspiracy and breach of contract.

In seeking to quash the case, lawyer Vicki Greco of Collinson Law says her client was exercising her First Amendment right to free speech and was emboldened by the .MeToo movement.

"She feels like this is another attempt to assert some type of power or abuse," Greco said Monday of Glass, who moved to Los Angeles.

"To me it's just another manoeuvre of manipulation because the evidence that they have presented is thoroughly lacking for him to refute any of this."

Kath has denied allegations of abuse. None of the allegations have been proven in court.

Greco's motion to dismiss the case will be heard Feb. 23.

On that date, Kath will have to prove a probability of winning his suit, in which he is demanding a jury trial.

Kath, who filed suit in November 2017, is seeking compensation including unspecified general, special and punitive damages.

The dispute traces back to October, when Glass posted a lengthy online message to fans alleging she was abused by Kath.

She wrote on her website that Kath abused her dating back to when she was 15 and he was 25.

She alleges he was manipulative and controlling during a relationship in which he gave her drugs and alcohol, and that she suffered physical and emotional abuse that included non-consensual sex.

A loss for Glass would not only be devastating for her claims, but would have broad implications for the burgeoning movement of female empowerment, says Greco.

"It would tend to make women think twice before they mustered enough courage to come out," she says.

"Obviously, it's very difficult to come out and report an event that occurred and you haven't talked about it for whatever reason -- there's myriad reasons women don't come forward -- but then once you get over that hump then you have to think, 'Oh, someone's going to sue me.' It's devastating.

"If the ruling is in our favour, obviously, it would be very helpful for other women and victims to feel empowered and not have to worry about the repercussions of coming forward."

Toronto police said Monday that an investigation of Kath by the sex crimes unit is ongoing.

A lawyer for Kath did not immediately respond to an interview request on Monday.