BOSTON — Prosecutors urged a judge Friday to sentence a Massachusetts chemist to up to seven years in prison if she pleads guilty in a drug-testing lab scandal that jeopardized thousands of criminal convictions and cost the state millions.

Annie Dookhan, 35, of Franklin, faces a long list of criminal charges, including tampering with evidence, obstruction of justice and perjury for alleging faking test results at a now-closed state lab.

Dookhan’s lawyer, Nicolas Gordon, pleaded for leniency, saying Dookhan’s only motivation was to be “the hardest-working and most prolific and most productive chemist.” Gordon said “this whole mess” began when Dookhan failed to follow certain lab procedures in trying to test more samples.

When she got caught, she panicked and tried to cover her tracks, Gordon said.

He said she never thought her actions would send the state’s criminal justice system into a “tailspin,” with more than 1,100 criminal drug cases dismissed or not prosecuted because of evidence tainted by Dookhan’s alleged actions and other fallout from the closure of the lab.

“This is not a woman who ever set out to hurt anyone,” Gordon said.

Dookhan, who has shown no visible emotion during previous court hearings, cried when her lawyer described her love for her 7-year-old son while asking for leniency.

Gordon said Dookhan is terrified of going to jail and leaving her son, who has some health issues.

“Her son is her life,” Gordon said.

Gordon said Dookhan has already been punished personally and professionally. He said her husband left her a month ago and is now living with another woman. Her career is over, he said.

“This woman’s life is destroyed,” he said.

But Assistant Attorney General Anne Kaczmarek called Dookhan’s motives “selfish,” and said her actions have “weakened the criminal justice system.” She urged the judge to sentence Dookhan to five to seven years in state prison.

The court proceeding was unusual because it was held in open court. Typically, such lobby conferences are held at sidebar or in a judge’s chambers and are designed to give defendants a sense of their likely sentence if they plead guilty.

Judge Carol Ball said she wanted to hold the proceeding publicly because the lab scandal has had such a serious impact on the criminal justice system that she felt it was important to resolve the case “with everything being open and up front.”

Ball told Dookhan’s lawyer she found it hard to believe that Dookhan did not foresee the consequences of her actions.

She said Dookhan’s behavior struck her as a sign of someone with low self-esteem who was trying to look “cool” by pumping up her reputation at work.

“This is sad, pathetic behavior, frankly, but the extraordinary damage is just incalculable,” Ball said.

Ball asked if Dookhan’s actions were motivated by a desire to “get these bad guys off the street.” Kaczmarek said investigators found no evidence of that.

Kaczmarek said the fallout from Dookhan’s alleged actions has cost the state “hundreds of millions of dollars” to try to assess the scope of the tainted evidence and to mitigate the effect on thousands of people charged with drug offenses during the nine years Dookhan worked at the lab. The court system has been deluged with motions for new trials filed by defendants who may have been affected.

State officials have estimated that Dookhan tested samples involving more than 40,000 defendants during her years at the lab.

In an interview with state police, Dookhan acknowledged that she engaged in “dry labbing,” when she would assemble a large collection of samples from different cases, test only a few of them, but label all of the samples as positive for illegal drugs.

She previously pleaded not guilty to 27 criminal charges.

Ball said she will consider the sentencing recommendations made by both sides and decide next week about what sentence she would give Dookhan if she changes her plea to guilty.