Some people who know Ryan Thomas Furlough described him as a shy, quiet young man from Howard County with apparently only one good friend.

But prosecutors allege that Furlough, 19, is a calculating murderer who poisoned that friend -- Benjamin Edward Vassiliev, 17 -- by spiking his Vanilla Coke with cyanide as the two Centennial High School classmates played video games in Furlough's basement.

In opening statements yesterday in Furlough's trial in Howard County Circuit Court, State's Attorney Timothy J. McCrone told jurors that Furlough was consumed with jealousy over Vassiliev's girlfriend and plotted the January 2003 killing for two months before ordering the poison over the Internet. He committed an "evil betrayal of friendship," McCrone said.

But defense attorneys said Furlough was in a suicidal "downward spiral" at the time, made worse by high doses of the antidepressant Effexor and the fact that Vassiliev had become too busy with other friends to have much time for Furlough.

"What Ryan has done has totally destroyed him," said defense attorney Jan O'Connor as Furlough sat staring downward. "He's not really here anymore. It's tragic because both Ben and Ryan have been taken."

Furlough, thin and blond with wire-rimmed glasses, is being held in the Howard County Detention Center. He was indicted on a first-degree murder charge Jan. 29, 2003. Vassiliev, a popular student who was active in Centennial High's drama department, went into a coma after drinking the cyanide-laced Vanilla Coke on Jan. 3 and died five days later.

In the trial, Furlough will not dispute that he killed Vassiliev, his friend since middle school, O'Connor said in an interview. Evidence against Furlough includes a videotaped statement to police in which he admitted to the crime. The video is expected to be played in court today.

O'Connor said the defense probably will ask Judge Raymond J. Kane Jr. to instruct the jury that it may consider the lesser charges of second-degree murder, punishable by up to 30 years in prison, and manslaughter, which carries a possible 10-year term. Prosecutors are seeking a first-degree murder conviction and a sentence of life in prison without the possibility of parole.

In her opening statement, O'Connor repeatedly referred to Furlough as a lonely student who was failing and had difficulty making friends. Although he had been seeing a psychiatrist since 10th grade and his mother had met with school counselors, Furlough's depression was unabated, O'Connor said. She said increasing doses of Effexor, prescribed by his doctors, gave him insomnia and suicidal thoughts.

A breaking point came in December 2002, when Vassiliev did not give Furlough birthday or Christmas presents, O'Connor said. "He lived in darkness. He lived in a world of no hope," she said. "He made a terrible, terrible, terrible choice to kill himself and to kill his best friend."

But prosecutors, describing Furlough as "diabolical" and "cowardly," tried to focus jurors' attention on what they said was the meticulous planning of Vassiliev's death.

McCrone said that in a letter Furlough wrote to Vassiliev in June 2002, he declared his love for Vassiliev's girlfriend and said, "I will never give up until I have the key to her heart."

In September, Furlough started doing Internet searches on poisons, McCrone said. In late November, he made arrangements to buy cyanide, using his mother's credit card, from Antec, a Louisville company that supplies the substance for use in electroplating and photography.

The package arrived Dec. 11, Furlough's 18th birthday. Soon after, McCrone said, Furlough offered Vassiliev a bottle of water after their chemistry class. Vassiliev took a sip and spit it out. McCrone said Vassiliev apparently had tasted the bitter almond-like flavor of cyanide.

On the night of Jan. 3, Vassiliev drank most of the can of Vanilla Coke that Furlough offered him, McCrone said. Then, McCrone said, as Vassiliev collapsed into seizures, Furlough slipped a vial of cyanide into his friend's shopping bag, to plant evidence of suicide.

Yesterday, Vassiliev's mother, Karen Dale-Barrett choked back tears as she testified about her son's relationship with Furlough.

Sitting near a courtroom display of a photo of the shaggy-haired Vassiliev in his formal senior class portrait, Dale-Barrett said: "Ben was a good friend. Ben was the best friend anyone would have. He was loyal."

Benjamin Edward Vassiliev went into a coma and died after drinking a cyanide-spiked Vanilla Coke.The defense stressed Ryan Thomas Furlough's despair. Prosecutors emphasized his calculation.