A decision not to charge a police officer who killed a five-year-old boy while driving over the speed limit has exposed a lack of transparency in the way Quebeckers are informed about deaths involving police.

Justice officials in the province are under no legal obligation to explain why the Sûreté du Québec officer will not be charged after he allegedly exceeded the posted speed limit by 72 kilometres an hour while on routine business in a Montreal suburb and struck a car, killing the child in the back seat.

In other provinces, including British Columbia, Alberta and Ontario, an independent body investigates deaths, serious injuries and other high-profile cases that involve police officers. If no charges are laid, investigators give relatively detailed summaries of facts and reasons.

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In Quebec, neighbouring police forces investigate such cases and provincial Crown prosecutors decide on charges. The prosecutors declined to explain their decision in this case on Wednesday. Late in the day, the prosecutors' office said in a statement that officials will meet the child's family in coming days and might reveal more details later.

The boy's parents, opposition politicians, advocates for police transparency, and even the police union were united on Wednesday in calling for prosecutors or Justice Minister Stéphanie Vallée to explain the decision.

Ms. Vallée admitted prosecutors mishandled one portion of the case by sending police officers to tell the family no charges would be laid instead of doing it themselves. But she said prosecutors followed their rules and the law in arriving at the decision not to lay charges.

"The situation is somewhat unusual in that a representative of the prosecutors' office should have accompanied the police" to inform the family, Ms. Vallée told the National Assembly on Wednesday.

Alexandre Cloutier, the Parti Québécois justice critic, asked Ms. Vallée to explain the circumstances of the crash and the rationale for the decision, as she is entitled to do under the law. She declined.

Mike Belance was driving with his five-year-old son buckled into the back seat in a residential area on Feb. 13 when an unmarked police cruiser travelling at high speed crashed into their Kia sedan.

The 29-year-old officer was driving 122 kilometres per hour in a 50-kilometre-per-hour zone, and was not responding to a call or other emergency at the time, La Presse reported on Wednesday. The Sûreté du Québec officer was on his way to relieve a surveillance team, the paper said in the report, citing confidential sources.

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The provincial prosecutors' office has refused to confirm that or provide other details.

Stephanie Thorne, the mother of the child, said she does not question the quality of the investigation conducted by Montreal police, but the family needs an explanation and an apology. Ms. Thorne said authorities seem to think the way her son died was normal.

She said the family is asking that the name of their son not be published. "We want to let him rest in peace," she said in a brief conversation.

Several Quebec governments have promised to establish an independent investigative unit for cases involving police, but it has been slow to get off the ground with a quick succession of elections in recent years.

The Liberal government has promised Quebec will have an independent investigation unit by 2016. The Justice Minister said the prosecutions office has additionally promised "to review its communications policy for decisions whether or not to lay charges."

Police unions have called for more information to be made public on police-involved investigations, said Paulin Aubé, a vice-president of the Quebec police officers federation. "We also want transparency, we are tired of being made to look crooked," Mr. Aubé said in a news conference on another matter. "We're not the problem. Quebec City is the problem. They've told us the prosecutors' office does not want to go there."

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Quebec prosecutors have occasionally shown more transparency after intense public pressure or political intervention. After police shot 18-year-old Fredy Villanueva in 2008, triggering a riot, prosecutors held a news conference to explain the decision not to lay charges, saying the officer feared for his life.