For five years, Adrienne Miranda has been on a crusade to prove that the death of her son — crushed under a Bobcat earthmover while on the job, his body face-down in the dirt under a hot summer sun — was no accident.

The mother from Lutherville has made claims of shoddy detective work and has alleged a sweeping coverup by authorities who don't believe a crime was committed against her 19-year-old son, Joseph A. Miranda.

She has irritated and at times angered a cadre of police, prosecutors and bureaucrats. She has sent endless emails, insisted that meetings with officials be recorded, provided names of people she felt needed to be interviewed, taken the police and others to court, lobbied the news media and picketed a state's attorney.

Miranda makes no apologies. Despite rulings from prosecutors in three counties and two police agencies that her son's death in July 2006 while working at a Hampstead landscaping company was a tragic accident, she has pushed on, ignoring repeated declarations of "case closed."

She accuses Baltimore County's top prosecutor of "preventing us from getting a fair trial and justice for Joseph." She wrote in one of several emails to The Baltimore Sun of her "continued torment, agony and living hell" and of her hope that the truth "for my precious son will be revealed and exposed."

Then, in August, Adrienne Miranda's persistence paid off. Baltimore County police were forced to add Joseph's name to their annual tally of killings — officially the 18th of 2011 — after the state medical examiner determined that he died "at the hands of another."

Her son's death was ruled a homicide.

The pathologist concluded that it was impossible for the young man to have been killed the way police said he was — slipping off the Bobcat and falling between the wheels as the skid loader lurched forward. Rather, the medical examiner concluded, Miranda was likely pushed or knocked to the ground just before the driver backed over his head.

"There is no plausible explanation as to why Mr. Miranda was in a face down position, while run over by the Bobcat," the assistant medical examiner wrote to the Baltimore County state's attorney. It was one of several factors discovered over the course of years that caused him to rethink the case.

"As the death was caused by the action of another person," the examiner wrote, "the manner of death is best re-classified as a homicide."

For a grieving mother, the surprise ruling breathed new life into her campaign to get someone charged criminally in the death of her son.

But the ruling was by no means an end to her quest for answers.

In fact, Baltimore County police and prosecutors said the medical examiner's ruling changes nothing. Scott D. Shellenberger, the state's attorney for Baltimore County, said there will be no further inquiry, no arrest, no grand jury, no trial, no criminal charges.

"I respectfully disagree with the conclusion now reached by you that Mr. Miranda's death was at the hands of another," he wrote the assistant medical examiner who handled the case, Dr. Zubiullah Ali.

In an interview after the new ruling, Shellenberger said, "The incident doesn't rise to the level of a crime."

After graduating from Towson High in 2005, Joseph Miranda worked at Watson's Nursery on York Road, nearly across the street from where he lived and grew up on Melton Road. He wanted to be a landscape architect.

A few months later, he took a job at Outside Unlimited, a large commercial and residential landscaping and irrigation company that at the time employed 175 workers sculpting gardens and lawns at homes, private businesses and university campuses. Its owner did not respond to repeated request for an interview.

Miranda took a liking to many of the Hispanic laborers, to whom he would give rides when he saw them walking to work. He often told his mother, "I'm going to be real hungry tomorrow, make me 10 sandwiches." They were for the immigrant workers.

On July 20, 2006, at the end of his shift, Miranda, then a foreman, had to load 20 trees into a truck to be planted the next day at Windsor Mill Middle School. He approached Paul Christopher Godwin, who was watching Antonio Rubio maneuver a Bobcat, loading dirt from a pile into a dump truck.