Three people went on trial on Monday in connection with the death of a six-year-old boy savaged by three pitbull terriers near Zurich last December.
The prosecution is contending that the boy's death could have been prevented had the accused acted correctly and responsibly.
Also in court for the trial in Zurich are the boy's parents and a 26-year-old woman who witnessed the attack and who has since had chronic post-traumatic stress.
The dog owners stand accused of manslaughter and of causing grievous bodily harm through negligence.
The prosecutor, Susanne Steinhauser, is seeking a prison sentence of two-and-a-half years for the principal accused, a 42-year-old Italian, a suspended sentence of 16 months for his 29-year-old Swiss girlfriend and a suspended sentence of 14 months for the owner of the flat where the couple lived with their dogs.
The charges, published last month, cover in detail the victim's ordeal on the morning of December 1, 2005 and how another boy narrowly avoided a similar fate.
A mother had taken her child to school and was returning with her younger son when three pit bulls suddenly appeared. The dogs adopted an attacking stance and surrounded them for more than a minute. The mother and son managed to remain motionless.
Then the six-year-old boy arrived, walking along the path to school. The dogs focused on him before running towards him. He tried to run away but the dogs jumped on him.
The boy sustained grave head and neck injuries and was most probably already dead by the time the dogs stopped their attack, according to the prosecutor.
The mother who witnessed the attack was very shaken up and has not been able to work since.
The prosecution aims to prove that the negligence that led up to the events was almost systematic.
Before escaping, the dogs were kept in a makeshift shelter on the flat's terrace. Five dogs had a total of 3.75 square metres to move around in. They had no difficulty in moving the planks and gaining access to the road.
The ten-month-old pit pulls had been imported, legally, from Italy two days previously. Since their birth they had been confined with two other dogs in a single room occupied by the mother of the principal accused.
The dogs had never seen another human being, had never been taken for walks and showed signs of having injured one another.
The prosecutor claims that the accused would have been able to save the victim's life – "with a probability that verges on certainty" – if he had respected his duties and responsibilities as a dog owner.
His girlfriend was subject to the same charges since she looked after the dogs in the same capacity as her boyfriend.
What's more, after the attack she managed to recapture two of the five escaped dogs but then returned to the flat rather than tend to the victim.
The flat owner, a 39-year-old Swiss who had just bought one of the pit bulls, faces the same charges. He saw the dogs escape but did not alert anyone, losing valuable time in finding them.
The trial is expected to last until Thursday or Friday.
swissinfo, Ariane Gigon Bormann in Zurich
Dangerous dogs came under the spotlight after the death of a young boy bitten by pit bulls last December in canton Zurich.
Parliament called on the government to strengthen federal legislation. The Zurich tabloid Blick, which launched a petition to ban pit bulls, collected more than 175,000 signatures.
Some cantons decided themselves to tighten their dog laws.
At the federal level, the law on the protection of animals is making it compulsory from next year for all dogs to have a tattoo or microchip.
Swiss legislation on dogs is among the least restrictive in Europe. Certain breeds are totally banned in France and Germany.
According to a Federal Veterinary Office report dating from 2002, about 13,000 people are bitten by dogs annually in Switzerland.
In 24% of cases, the victim is bitten by his own dog, in 34% the dog is known to the person bitten, and in 42% of incidents the dog is unknown to the victim.
Before the young boy's death in canton Zurich, the only fatality blamed on a dog dates back to November 2000 in Zurich. A woman who had been frightened by a dog jumped into the River Limmat and drowned.