The six-year saga of the so-called Widener slasher neared an end yesterday as a jury heard closing arguments in Middlesex Superior Court.

The prosecution is seeking to prove that Stephen L. Womack, a former Widener Library employee who has admitted to sending extortion letters and ravaging hundreds of thousands of dollars worth of books, is guilty of attempted extortion and willful and malicious destruction of property.

The prosecutor, Anthony Gemma, stressed that Womack was motivated by revenge and acted with malicious intent.

"This case is based on deliberate choices made by the defendant," said Gemma, the assistant district attorney, in his closing argument. "It is a case about hatred, the desire to control others....It is a case about revenge."

The defense argued that Womack did not intend to follow through with his threats to extort money or commit physical violence, thus rendering him not guilty of extortion and malicious destruction.

Although Womack has pleaded guilty to slashing the books, the jury must decide if he destroyed property with malicious intent and intended to follow through with threats he made in several letters, according to instructions from the judge.

Between 1990 and 1992, Womack used a knife and his hands to mutilate hundreds of rare books--including many written in esoteric languages and others related to early Christianity, sagas and organic chemistry--in the Harvard and Northeastern University libraries.

In one of his five letters, Womack threatened to blow up Widener and Northeastern's Snell Library if Jewish staff members were not fired.

In another, he said he would bomb the Belmont Bank if ransom money was not left for him in the Widener stacks.

In his testimony on Monday, Womack--who has a virtually inaudible voice and a unique, long-armed gait that has spawned his courtroom nickname, "Thumper"--told the jury, "I stole those books as...retaliation against the system."

The prosecution argued that Womack's testimony is evidence of malicious intent.

"The defendant quite candidly admitted to [committing crimes] to exact revenge," said Gemma.

But the defense argued that Womack's anger toward "the system" stemmed from his involuntary stays in a series of mental hospitals and not from a desire to seek revenge against the universities.

According to William P. Homans '41, Womack's defense attorney, Womack was forced to spend a year and a half "under lock and key" in two Massachusetts hospitals after he had served a six-month jail sentence for a 1987 crime.

"[Womack] told the doctor that he would commit a wrongful act for every day of his forced confinement," Homans said.

The prosecution buttressed its argument that Womack maliciously intended to cause harm by showing how Womack's letters were infused with specific locations and incidents.

"He made the letters serious by incorporating real events" Gemma said, "details of bodies buried in real places, specific instructions to leave money in specific places--[thus making people] believe he is deranged and dangerous, and forcing them to act against their will."

But defense lawyer Homans argued that Womack's letters were so far removed from the reality of Womack's life that "a reasonable person would have a difficult time believing that he had intended to [follow through with his threat to] extort money, hurt people or make people act against their will."

Homans cited the fact that Womack never picked up his ransom money--although FBI agents planted it in obscure locations in Widener, as requested--as further evidence that Womack was merely trying to cause a disturbance and not intending to extort funds or cause violence.

Although Womack has made comments such as, "I won't stop [my assault against the system] until the voices tell me to stop," Homans' said Womack did not plead insanity in the case because a psychiatrist diagnosed him with a severe personality disorder, not a psychotic disorder.

The jury was instructed, however, that it could consider the possibility of mental imbalance when coming to its decision.

The jury's decision will culminate a four-year investigation conducted by Harvard and Northeastern police forces and the FBI.

"It was a very high-profile case, and good basic police work went into resolving it," said Harvard Sgt. Kathleen M. Stanford. "I know we have the right man, and now it is up to the jury to find [him guilty]." Stanford and Lt. John Rooney spearheaded the Harvard police force's effort to apprehend the Slasher.

Associate Librarian of Harvard College Lawrence E. Dowler said Womack's actions have served as a "wake-up call" and said the library has strengthened security as a result.

Greer Gillman, an expert witness who worked for the preservation of books at Widener during the period of the slashings, said she has spent hundreds of hours identifying Harvard's decimated volumes.

"It was a wonderful intellectual puzzle but horrific to realize the extent of the damage to the collection," Gillman said. "We'll be finding mutilated books for decades.