BOSTON — Prosecutors asked that a chemist charged in a far-reaching scandal at a Massachusetts drug-testing lab serve five to seven years in state prison if she pleads guilty in a case that has jeopardized thousands of criminal convictions.

Annie Dookhan has caused “egregious damage” to the state’s criminal justice system, the attorney general’s office wrote in a sentencing memo filed in court Thursday. A defense lawyer said he would seek a year in jail for his client.

Dookhan is charged with obstruction of justice, perjury and tampering with evidence while working at a former Department of Public Health drug lab. The lab was shut down in August 2012 after state police investigated its practices. Since then, at least 1,100 criminal cases have been dismissed or not prosecuted because of tainted evidence or other fallout.

In the sentencing memo, prosecutors from Attorney General Martha Coakley’s office said Dookhan deliberately skipped vital steps in the drug-testing process and ensured that samples sent to the lab by police departments would test positive for drugs to “improve her productivity and burnish her reputation.”

“The gravity of the present case cannot be overstated,” Assistant Attorneys General John Verner and Anne Kaczmarek wrote. “The defendant’s actions not only affected the particular individuals named in the indictments but also the entire criminal justice system in Massachusetts.”

The memo was filed in advance of a so-called lobby conference Friday in Suffolk Superior Court in Boston. During the conference, prosecutors and Dookhan’s lawyer, Nicolas Gordon, are expected to meet with Judge Carol Ball to discuss sentencing recommendations if Dookhan were to plead guilty.

Gordon said he plans to recommend a one-year sentence, followed by any amount of probation and whatever conditions the judge imposes. Prosecutors said they would recommend five years of probation.

“I feel the appropriate period … is one year” in county jail, Gordon said Thursday, confirming that “a possible resolution of the case” will be discussed in court Friday.

In their memo, prosecutors said state sentencing guidelines call for a sentence lower than what they are recommending – one to three years – but they said the judge should consider the extensive repercussions of Dookhan’s alleged conduct.

They said that at least 51 people who were released from custody because of tainted evidence have been re-arrested on new charges, including a Brockton man who is now charged with murder.

In addition, the state has spent millions of dollars to calculate the damage caused by Dookhan’s alleged misconduct and to attempt to mitigate the effect on thousands of people charged with drug offenses during the nine years Dookhan worked at the lab, they said.

“Given that the motives for the defendant’s actions were selfish and shallow, coupled with the egregious damage she created for those reasons, significant incarceration is warranted,” prosecutors wrote.

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

She signed a statement for state police in which she admitted making some negative samples positive for narcotics and “dry labbing,” or testing some samples for drugs and assuming others were positive. She has pleaded not guilty to 27 charges.

The conference scheduled Friday does not mean Dookhan will definitely change her plea to guilty.

In their memo, prosecutors said they were making their sentencing recommendation “in contemplation of the defendant accepting responsibility and pleading guilty.”

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