HALIFAX -- A Crown prosecutor says he has a "good case" against four British sailors charged with sexually assaulting a young woman at a military base in Halifax.

"We wouldn't be here if we didn't think it met the realistic prospect of a conviction. Obviously we're going to push it forward as far as the evidence allows," said Scott Morrison outside court on the first day of the preliminary inquiry Friday.

Simon Radford, Joshua Finbow, Craig Stoner and Darren Smalley are all facing a charge of sexual assault causing bodily harm.

All of the men appeared in court wearing suits and with separate lawyers representing them.

When they were arrested last April, the men were in Nova Scotia to participate in a hockey tournament with local Armed Forces personnel.

The Crown alleges they participated in a group sexual assault last April 10 in a barracks at CFB Shearwater.

They were staying at CFB Stadacona, but were asked to leave last May and relocated to another military base in Alberta where there is a British army training unit.

A judge ruled in August that three of the men -- Stoner, Finbow and Radford -- would be permitted to return to the United Kingdom while awaiting the beginning of the preliminary hearing. Smalley was permitted to return to his home under similar conditions after a separate hearing in September.

Morrison said outside court that all of the men had returned to Halifax five days prior to the hearing, as required by the Nova Scotia Supreme Court.

The main purpose of the hearing before provincial court judge Timothy Gabriel is to test the Crown's case to determine whether the case against the men will be committed to trial.

"At the end of the day the court will be asked determine whether some, none or all of these men will be be sent to (Nova Scotia) Supreme Court for trial," he said.

Morrison said the Crown expects to call 10 to 15 witnesses, including the female complainant, during the five days scheduled for the hearing.

There is a publication ban on all of the evidence presented in court.

Eric Taylor, the second Crown working on the case, led the questioning as the first witness appeared on Friday.

The case is proceeding in a civilian court because the offences were allegedly committed against a female civilian and the men were off-duty at the time.