A guilty verdict in one of New Jersey's most infamous cold case killings should be overturned because of a judge's missteps and a lack of evidence presented by prosecutors, attorneys for the woman convicted of the crime argued before an appeals court Monday.

Michelle Lodzinski is serving a 30-year sentence for killing her 5-year-old son, Timothy Wiltsey, in 1991 in a case that took 25 years to come to trial. Lodzinski was considered a suspect from the outset after the boy disappeared, due to her shifting accounts of what happened on the last day he was seen.

That gap was the basis for one of the arguments Lodzinski's attorneys made Monday. Gerald Krovatin told the three-judge panel that bringing the charges so long after the fact violated Lodzinski's due process rights.

Lodzinski told investigators that her son disappeared while they were at a carnival in Sayreville in May 1991, and she told varying accounts describing strangers who could have kidnapped him.

The case went cold for nearly 20 years, until Lodzinski was arrested in 2014 at her home near Port St. Lucie, Florida. Investigators said a break in the case had come when one of Wiltsey's former babysitters identified a blue blanket, found near the boy's body 11 months after he disappeared, as belonging to Lodzinski. A cause of death couldn't be determined because his body had deteriorated.

The blanket is at the heart of another contention by Lodzinski's attorneys, however: It contained no trace evidence or DNA tying it to either Wiltsey or Lodzinski, and no other evidence presented by prosecutors tied her directly to his death, Krovatin argued.

"The circumstantial evidence doesn't permit a logical and reasonable inference that she caused his death, or did it knowingly," he told the three-judge panel. The evidence is more consistent with an accidental death, he said.

Assistant Middlesex County Prosecutor Joie Piderit countered that the balance of the evidence led to only one conclusion.

"You have to take the evidence in its totality," she said. "There's no smoking gun, there's no bullet, there's no confession. But there's a lot of pieces of evidence that point to the defendant's guilt.

"This is a cold case, and this is how cold cases go," she added.

The other main point of contention concerned state Superior Court Judge Henry Nieves' dismissal of the jury foreman during deliberations, after it was revealed the juror had done Internet research on FBI crime-scene guidelines and shared his findings with other jurors. An alternate stepped in and the panel reached a guilty verdict several hours later.

The juror's actions didn't merit a dismissal, Krovatin and co-counsel David Fassett argued Monday. But if they did, they contended, that meant the whole jury was tainted and Nieves should have declared a mistrial.

The appeals court is expected to rule in the next few months.