A Canadian woman's detention for months in a Mexican jail without being formally charged has raised some questions about Mexico's criminal law system and procedures.

Cyndy Vanier and three others, who are suspected of being involved in a plot to smuggle members of Libya's Gadhafi family to Mexico, have been detained for 80 days.

But the detention is perfectly legitimate under Mexico's "preventive arrest" laws, also known as "arraigo." Under these laws, a judge can grant a prosecutor an "arraigo order." This gives the prosecutor the authority to hold up to 80 days those suspected of committing serious federal offences (usually related to organized crime) and allows them more time to gather evidence.

After the 80 days, the suspect must either be released or be formally arrested (face charges) and have their case put before a judge. The judge will then have 72 hours to decide whether a trial should proceed.

Confusing? Maybe. But just one example of how Mexico's criminal law system differs from Canada.

On its website, Foreign Affairs offers a number of pointers for Canadians who may find themselves embroiled in Mexico's legal system, warning that those accused could face a lengthy time in detention until the judicial process runs its course.

Canadians, like other foreigners in Mexico, are entitled to certain rights upon arrest. This includes being provided with an interpreter, the right to have Canadian authorities notified and the right to communicate with and have access to a consular officer.

A person arrested in Mexico will either face federal or state charges, depending on the alleged offence.

Federal offences include terrorism, drug trafficking, money laundering and child pornography and are prosecuted by the public ministry (Ministerio Publico).

State/local offences include murder, attempted murder and theft. Drunken tourists acting disorderly are generally considered to be committing an infraction, not a criminal offence — the consequences usually being a fine or up to 36 hours of arrest.

With federal or state criminal offences, the public ministry will conduct a preliminary investigation, usually taking a couple of days, to gather evidence to support an allegation.

"When information is gathered and the office believes it has grounds to support an accusation, [the public ministry's] role changes and starts working as a formal prosecutor like in Canada … and stops working as investigator," said Guillermo Cruz, a Mexican legal consultant now based in Toronto.

3 possible decisions

The ministry will put the case before a judge who has 72 hours to decide if the prosecutor provided enough information and evidence to support a case. (The suspect can ask for the time period to be extended for another 72 hours, if they think it will help their case.)

After the 72 hours, the judge must render one of three decisions: the accused is to proceed to trial, the accused proceeds to trial under different charges, or the accused should be released due to lack of evidence.

If the judge believes there's enough evidence for a trial, a detention order will be issued. Bail is not common and not an option for those accused of serious criminal offences like murder or attempted murder.

Trials are much different than those in Canada. As Cruz said, the judge "is the trier of fact and the trier of law" meaning no jury is present. The judge decides whether the defendant is innocent or guilty and imposes the sentence.

The first stage of a trial is conducted over several hearings where arguments and witness testimony are written down — there is no live testimony from witnesses or lawyers. The judge is not actively involved in this process, unless serious disputes arise, according to Foreign Affairs.

There are also no courtrooms. The accused "usually watches from a protected area while the lawyers and court officials huddle around a typewriter or a computer, often for hours at a time," according to Foreign Affairs.

Judge reviews case

The judge will then open the next stage, or the conclusion stage, of the trial and ask the prosecutor to provide the specific accusation against the accused and propose a penalty based on all the evidence. The defendant will reply to the accusation and will be able to give evidence supporting their innocence.

Cruz said the judge then declares the case closed and moves to the sentencing stage, where the judge reviews the whole case and decides guilt or innocence of the defendant and the penalty.

For federal offences, the trial must be conducted within 10 months, with the judge given an extra two months to reach a decision.

Cruz said the trial duration for state offences can differ, depending on the state, but shouldn't take more than a year.

But a judge has only four months to reach a verdict when the maximum possible sentence is less than two years.

The defendants can also appeal their verdicts.