A Canadian diplomat's teenage son charged in a double killing in Florida that left his older brother dead is now expected to be tried in November at the earliest.

In the interim, Marc Wabafiyebazu, 15, of Ottawa, is getting set to appeal a Miami judge's ruling that denied him bail pending his murder trial.

Wabafiyebazu, the son of Canada's consul general to Miami, Roxanne Dube, is locked up in a 1,300-bed adult detention centre, where most contact visits are barred and where he is the youngest inmate.

"He's hanging in there as best as can be expected under these unfortunate circumstances," said lawyer Curt Obront, who saw him this week.

Now that the judge's formally signed no-bail order has been received, Obront said he would be "appealing imminently."

Wabafiyebazu was arrested March 30 outside an apartment in which his 18-year-old brother Jean Wabafiyebazu and another man, Joshua Wright, 17, were shot dead. Two other men, including an alleged drug dealer, were injured.

Police allege the younger sibling confessed that he and his brother had gone to rip off the dealer, but the armed robbery had gone sour.

The defence has argued that the testimony of a rookie officer, who reported the purported confession, was "absurd" and was possibly the result of his desire to get in on a big case.

A spokesman for the Miami-Dade state attorney's office said this week that a tentative trial date has been set for Nov. 2. Prosecution and lawyers were also expected to update the court on their progress at a status hearing in September. Wabafiyebazu has previously pleaded not guilty.

While the prosecution does not allege Wabafiyebazu shot or even threatened anyone, Florida law allows for the felony murder charge if he was part of the armed robbery that resulted in the killings. Surveillance video shows that he remained outside until he heard the deadly gun shots and ran inside to see what happened.

Still, a grand jury indicted him as an adult, meaning he could face life behind bars if convicted.

At the bail hearing in May, Circuit Judge Teresa Pooler, who is an elected official, said granting him interim release was too risky given the possibility he could flee the United States and that she couldn't rely on Dube to keep proper tabs on him.

Wabafiyebazu also faces an armed robbery charge on which the felony murder charge is based.

Two other men charged in the killings, alleged drug dealer Anthony Rodriguez, 19, and Johann Ruiz-Perez, 21, have also pleaded not guilty to felony murder charges in the case. They are due for a status hearing later this month.

Dube, who sees him twice a week through glass and is allowed a contact visit once a month, refused to comment publicly.