John Grega sat on the front porch of his mother's Lake Ronkonkoma home Thursday, still dazed by the best news he's had in nearly 20 years: He's no longer accused of his wife's killing.

"I'm in shock, total shock," he said. "It really is so much to process."

Prosecutors dismissed the aggravated murder charge on Wednesday, opting not to move ahead with a court-ordered retrial based on new DNA evidence.

Grega, 51, who had spent 18 years in prison, suddenly found himself fielding congratulatory phone calls and visits from overjoyed family members and friends.

Longtime pal David Reese walked up the driveway, hugged Grega and produced a cigar.

"I'm going to have a celebratory cigar with Mr. Grega," he announced.

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Grega said he didn't sleep much Wednesday night after getting the news. Siblings and other relatives rushed over to his mother's home on a quiet, tree-lined street.

Marion Grega, 73, said her son, a former NASA contract engineer, sat in the backyard gazing at the stars. "He can't believe he has his freedom," she said.

After taking his ailing mother for treatment Thursday, Grega was thinking of going out to dinner and ordering surf-and-turf -- the same meal he had when he was released from prison one year ago.

"This is beyond my comprehension right now," he said. "It hasn't sunk in."

Grega was convicted less than a year after his wife, Christine Veal Grega, was found strangled and sexually assaulted on Sept. 12, 1994, in the West Dover, Vt., condominium where the couple was vacationing with their young son.

Sentenced to life without parole, Grega was released in August 2012 when new DNA evidence -- skin cells from an unknown man found inside the victim's body -- led a judge to overturn the conviction. Prosecutors filed a new aggravated murder charge in advance of a scheduled retrial.

In May, Windham County Superior Court Judge John Wesley gave prosecutors three months to complete advanced DNA testing of crime scene evidence other than the skin cells.

Unable to meet today's deadline, prosecutors dropped the charge. A joint notice of dismissal was filed Wednesday by the Vermont attorney general's office and Windham County State's Attorney Tracy Shriver.

In a statement, the prosecutors said the investigation will continue and new charges haven't been ruled out.

Christine Grega's family members could not be reached for comment.

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Grega's legal challenges were handled by the New England Innocence Project. Attorney Ian Carleton, part of the defense team, said Thursday that Grega "fought unwaveringly to clear his name."

Carleton said the defense will be filing court papers next week seeking to have the case dismissed with prejudice, meaning Grega couldn't be charged with his wife's killing a third time.

Prosecutors at Grega's original trial relied exclusively on circumstantial evidence and his own statements to police that included conflicting accounts and admissions that some of his wife's injuries were caused by rough sex they had before her death, authorities said.

Since his release, Grega has been living with his mother, who has pancreatic cancer.

Thursday, she said she prayed for this day -- her son back home, no longer accused of murder.

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"It felt like this is coming to an end -- finally," she said.

Grega said he will continue to care for his mother but beyond that has no plans for the future. He expressed his gratitude for the tireless work of the New England Innocence Project and then ran out of words.

"I really can't say a heck of a lot, except how happy I am," he said.