Shooting-Case Defendant Is Portrayed as Insecure : Murder trial: The manhood of the high school dropout was threatened, a prosecutor tells jurors. Paul M. Crowder is accused of killing a basketball star on her prom night.

Paul M. Crowder, a high school dropout accused of killing basketball star Berlyn Cosman on her prom night, brandished a gun at a post-dance celebration to bolster his masculinity but turned deadly and shot Cosman when she insulted him, a prosecutor told jurors Monday.

On the first full opening day of Crowder’s murder trial, Deputy Dist. Atty. Christopher J. Evans portrayed the 19-year-old former Crescenta Valley High School football player as an insecure, threatening youth who repeatedly waved a .357 magnum and drunkenly pointed it at students celebrating their prom in the wee hours of June 1 at the Crown-Sterling Suites Hotel in Anaheim.

“The evidence will show he went there to shoot someone,” Evans told jurors in Orange County Superior Court. “Crowder brought that gun as his manhood, as his pride. . . . During the course of the evening, he had a serious injury to his manhood.”

Soon after Crowder and a friend arrived at the party, it “turned into every parent’s nightmare,” Evans said. He said Crowder jokingly loaded and unloaded the revolver, held it on his lap, gestured with it and pressed it into one teen-ager’s buttock, asking if he’d like it blown off.

Several teen-agers who attended the post-prom party in three hotel suites testified Monday that Crowder became angry after Cosman and a friend, Jill Cappillero, refused to let him party in the room where they were trying to sleep.

Mitchell Stroup, a 16-year-old who attended the party, testified that Crowder left the main party room at one point very late. About 20 minutes later, Stroup said, he heard Crowder yelling in the hallway.

“He was cussing, saying: ‘Then where am I gonna sleep? . . . I wanna party in here,’ ” Stroup said. “He walked back into our room cussing and mumbling under his breath . . . saying: ‘I hate those bitches. I’m gonna kill them.’ ”

Just before dawn, as the popular La Crescenta senior slept on a fold-out bed, Crowder returned to the room and shot her with one blast from the revolver, the prosecution alleges.

The bullet went through her head and lodged in the mattress. Cosman, an aspiring Olympic basketball player at Crescenta Valley High who had won an athletic scholarship to a Missouri college, died soon afterward.

The defense contends that Crowder stumbled in the doorway to Cosman’s room, accidentally discharging the gun. Prosecutors argue that Crowder is guilty of at least second-degree murder because he should have known his actions were reckless enough to result in someone’s death. When a gun is used, that charge carries a punishment of 17 years to life.

But Evans intends to present an additional theory of first-degree murder, based largely on a statement Crowder allegedly made that he hated Cosman and another girl and wanted to kill them. A first-degree conviction could mean 27 years to life.

The trial began Aug. 26 but was postponed while an appeals court considered a defense request for a postponement. That request was denied late last week, so the trial resumed Monday. The prosecution’s case should close within three days.

A parade of teen-age witnesses described a typical prom night party: About two dozen youths talked and played beer-drinking games in smoke-filled rooms while MTV blared on the television set. A few smoked marijuana or took LSD. They described some party-goers as “wasted,” others as “buzzed.”

Defense attorney E. Bonnie Marshall, who deferred an opening statement until later, focused on the drinking and drug use in her cross-examinations, implying that the witnesses might not be recollecting events accurately.

Questioning the homicide detective on the case, Marshall noted that most of the mattress in which the bullet was found has since been destroyed. She has said that mattress could prove that the bullet was fired from close to the ground, supporting her theory that Crowder was tripping as the gun was fired.

Cosman’s father, Mark, listened from one side of the courtroom, a few feet from where Crowder’s 10-year-old brother sat. He said he wants to know “the truth, once and for all,” even though it is painful to hear.

“A great sadness has come into our home,” Cosman said during a recess. “Something we would have laughed at a few months ago, there’s always that snap of pain. . . . I look at videotapes of her, and I want to dive into the television. I look forward to dreams at night when she and I are together.”

Crowder, who was working part time at a carwash, was invited to the party because some of the teen-agers feared that the jealous ex-boyfriend of one of the girls would show up and cause trouble. Brian Birk, 19, the girl’s prom date, testified that Crowder flashed a gun at him in the hallway of the hotel.

“He said: ‘I’m here to watch your back,’ ” Birk testified, adding that Crowder then pulled back his sports coat, revealing the butt of a gun tucked into his waistband. He said he thought Crowder was trying to be tough.

Another party-goer, Chad McClinton, 17, recounted for the jury how Crowder pressed the gun into his buttock as McClinton lay on his stomach watching television.

“He said: ‘It’s only loaded,’ ” McClinton testified. “He was joking around.”

Some of the teen-agers urged Crowder to put his gun away, and one took the bullets from him at one point. But most still described the environment as fun and easygoing, despite Crowder’s unpredictable actions with the revolver.

Joey Gobo, 17, a friend who drove Crowder to the party, testified that he wasn’t surprised when Crowder brought guns--one for himself and a 12-gauge shotgun for another friend. He said Crowder had been carrying guns on most occasions in the previous two weeks.

There was other testimony that implied Crowder was quite fond of guns.

Stroup said Crowder referred to the gun as “my baby . . . my bad .357.” And a couple of weeks earlier, Stroup said, Crowder splintered a vodka bottle with one blast, boasting: “That’s easy, watch this.”

Other teen-agers who attended the party were scheduled to testify today.