BOSTON (AP) -- As a girl and young woman, Annie Dookhan was quiet, unassuming, not one to wear makeup. She was charming but stood out more for her dedication to her studies, and by all accounts appeared headed for success.
The only child of hard-working immigrant parents, she enjoyed their pride as she glided through a prestigious Boston prep school, graduated from college with a degree in biochemistry and appeared headed for medical school.
Now, as she takes center stage in a shocking scandal that has sent the Massachusetts legal system into a tailspin, those familiar with her from school and work are struggling to reconcile the Annie Dookhan they knew with the chemist accused of falsifying criminal drug tests.
"I find it hard to believe that she was an individual who decided to falsify lab results ... that she would turn into someone who did something like that. ... That isn't the person I remember," said John Warner, an instructor who gave her A's and A-minuses in 2000 when she took his biochemistry class as a senior at the University of Massachusetts-Boston.
"Obviously, things can happen to people," he said. "Either something happened in her life that changed the person that she is, or this is a deeper story."
Dookhan's struggle with both personal and professional problems in 2009 -- including a miscarriage and a legal ruling that put new pressures on chemists at the lab -- may help offer an explanation, one former co-worker said.
"Perhaps she was trying to be important by being the go-to person," Elizabeth O'Brien told state police, who shut down the lab in August after discovering the extent of Dookhan's alleged mishandling of drug samples sent to the lab by local police departments.
In her own interview with police, Dookhan said she had not tested all the drugs she claimed she did, forged initials of her co-workers, and sometimes mixed drug samples to cover her tracks.
"I messed up bad; it's my fault. I don't want the lab to get in trouble," she said, according to a state police report.
She faces as many as 20 years in prison on obstruction of justice charges. More than two dozen drug defendants are already back on the streets as authorities scramble to figure out how to handle the cases of more than 1,100 inmates whose cases Dookhan handled.
State police say Dookhan tested more than 60,000 drug samples involving 34,000 defendants during her nine years at Hinton State Laboratory Institute in Boston.
Until recently, she had a reputation for diligence and hard work.
Born in the Caribbean nation of Trinidad and Tobago, Dookhan moved to the United States with her parents as a child and spent part of her youth in a working-class neighborhood in Stoughton, about 20 miles south of Boston. She later became a naturalized U.S. citizen.
Neighbors knew Dookhan, then Annie Khan, as a quiet teenager whose parents liked to share stories of her academic success.
"She seemed like an overachieving sort of kid," said Frank Clark, who lived down the street in the 1990s.
Clark's elderly mother also lived on the Khans' block, and Annie's father would mow her lawn and shovel snow from her sidewalk, without ever asking for thanks.
"They really were a nice family," Clark said.
In 1990, Dookhan started seventh grade at the elite Boston Latin Academy, the country's first college preparatory school for girls; now co-ed, it requires students to pass an entrance exam to enroll. Her father ran a handyman business in the same section of the city.
She enrolled in 1996 at Regis College, studying there for two years before attending UMass-Boston. As a biochemistry major, her face was familiar to other students who would come across her in the lab.
Nicole Lee, a biochemistry major who graduated with Dookhan in 2001, said her classmate was quiet and "a normal, sort of nerdy student."
Dookhan wore eyeglasses, didn't wear makeup and usually tied back her long, dark hair. While she had a feminine and charming manner, Lee said, it wasn't enough to make her really stand out.
"She wasn't really noticed, but you know her. Just good enough to know her and recognize her," Lee said. "I'm really surprised she's sort of related to this crime."
At UMass, Dookhan got top grades in Warner's biochemistry class during her senior year. He called her hardworking, quiet, smart and determined. He believed Dookhan had aspirations for medical school, and the college's 2001 yearbook shows her as a member of the Pre-Med Society and the Chemistry Club.
"Everyone is shocked," Warner said. "We can't believe it."
The year after she started working at the Hinton lab, she married Surrendranath Dookhan, a software engineer also born in Trinidad. They bought a house in Franklin, about 40 miles southwest of Boston, and had a son together in 2006. Branden Dookhan turned 6 this month.
Authorities so far can't find a motive for Dookhan's actions other than she wanted to be seen as a good worker, state Attorney General Martha Coakley has said.
But being a good worker became more complicated at the Hinton lab a few years back.
In 2009, a U.S. Supreme Court decision known as Melendez-Diaz grew out of a Boston drug case that said defendants had the right to cross-examine chemists in court who had prepared prosecution reports against them.
The decision meant chemists, including Dookhan, had to spend more time in court and less in the lab to keep up with the demands of the justice system.
"Annie was going through personal problems, then court, and Melendez-Diaz was tough at first on her. In 2009, she had a miscarriage and other personal problems," O'Brien, the co-worker, told state police.
Dookhan already had a reputation as the most productive chemist at the lab, logging such a high volume of samples that colleagues started questioning her work about four years ago.
In 2010, supervisors did a paperwork audit of her work but didn't retest any of her samples. They didn't find problems.
Dookhan had to send a resume to prosecutors whenever she testified in criminal cases. In 2010, O'Brien caught Dookhan padding her resume by claiming she had a master's degree in chemistry from the University of Massachusetts. She took it off her resume but later put it back on, O'Brien told police.
In August, another Hinton chemist told investigators her own monthly sample testing volume dropped from about 400 to 200 after Melendez-Diaz, but talk around the lab was that Dookhan was testing 800 a month.
Another colleague wondered in a police interview whether Dookhan had a mental breakdown.
Dookhan told investigators she was in the process of a long divorce, but there is no record of any divorce complaint filed at the Norfolk Probate and Family Court. She said she wanted to get her work done and never meant to hurt anyone.
After her March 2012 resignation, while facing an internal department probe, Dookhan told a fellow chemist she used to join for after-work drinks that she didn't want to get her in trouble, too. She told the woman not to call her anymore and to delete all her emails, text messages and records of their phone calls.
A man who worked with Dookhan at Mass Biologics in Boston for a couple years after her college graduation, Aaron Weagle, said she was a pleasant and friendly colleague and not the type of person to fabricate things.
Dookhan's job then was to perform identification tests on raw materials, what Weagle said amounted to basic chemistry, and was nearly as technical as her work at Hinton. He saw no warning signs, professionally or personally, that Dookhan was heading for disaster.
"She didn't make up stories to make people like her more. I never saw that," he said.
The chemist he has read about in news on the lab scandal seems like a different person.
"I cannot rectify it," he said, "with the woman I know."