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McKINNEY -- Adam Staup was a dutiful, mature, quick-to-do-as-he-was-told teen who was in the ROTC and volunteered for an animal shelter, a psychologist testified Tuesday.

But the 17-year-old, accused of helping a classmate carry out a murder plot, was also portrayed as someone willing to help to a fault.

'I get the sense that he wants to help people to his own demise, to his own martyrdom,' said Dr. Robert Lackey, a psychologist who examined Staup and his accused accomplice, Brenden Bridges.

Lackey's testimony came during a hearing where a judge will decide whether to certify Staup to stand trial as an adult in the strangulation of Staup and Bridges' Wylie East High School classmate Ivan Mejia.

The same judge certified Bridges to be tried as an adult last week.

Staup and Bridges are accused of hatching a plot to kill Mejia because Bridges wanted to get rid of his romantic rival. Investigators say the teens began planning the murder six days beforehand and dug a grave the day before killing Mejia. Authorities say Staup confessed to creating a fake profile on a messaging app to trick Mejia into thinking he was going to meet the object of the teens' affections when he was killed.

In court, Wylie East High School teacher Rebecca Lynch testified that Mejia and Staup both were in her theater class last spring.

She said Mejia and Staup typically sat together, even on the day before the murder. Lynch said Mejia was worried about a ticket that day because of how it might affect his standing with the Marines. Mejia had signed up to enlist after graduation. Staup told him that it wasn't a big deal and he shouldn't worry, she said.

When news of Mejia's death broke, Lynch said it was a 'very big shock' to find out Staup was accused of being involved.

'I just thought they were friends,' she said.

In court, Staup's mother and father were visibly emotional as Lackey testified about their son, who appeared to weigh about 25 pounds less than when he was arrested.

Lackey said the head of the ROTC described Staup as 'well mannered and respectful.' The staff at the animal shelter and the restaurant where he worked described him in much the same way.

He was a teen who had planned to join the National Guard and to get a social work degree. School staff members described him as 'capable, polite, respectful and service-oriented,' Lackey said.

'They were the stunned by this,' the doctor said.

Staup was described as constantly looking to be helpful, including to Mejia. Lackey said Staup told him that Mejia had previously come to him for advice about how he could improve his reputation.

He had suggested to Mejia that he join the ROTC, which Mejia did.

Lackey said anytime Staup greets someone, he would stand at attention and put his hand out to shake the other person's hand.

'His desire to help others tends to be some part of most of his decision making,' Lackey said.

His mother told Lackey that she had told Staup that she feared his friends were taking advantage of him.

'He tends to want to please people,' Lackey said.

Lackey said Staup told him it was Bridges who first came up with the idea of killing Mejia. He said Bridges formulated the plan based on his viewing of the TV serial killer show 'Dexter.'

The doctor said that Staup told him that, initially, he saw this as a revenge fantasy, and it wasn't until that they were digging the grave that he realized this was for real.

Lackey testified that Staup told him he was thinking, 'How do I get out of this?'

'He couldn't change his thought, because he felt obligated to do this,' Lackey said. 'He felt like he was too far into it. I believe he was looking for a way out to where he could still save face.'

Lackey's analysis of Staup tended to be more in keeping with the defense's portrayal of a gullible teen who was manipulated by a friend into committing an awful crime.

In court, prosecutors contended that Staup was just as culpable, given that he's the one that sent the message to Mejia to lure him there and that he was allegedly the one to first attack Mejia.

Lackey said Staup acknowledged Bridges would not have followed through with the plot without him.

'I think about Ivan a lot,' Lackey said Staup tearfully told him. 'I feel bad. He didn't deserve this to happen.'

Testimony is expected to continue throughout the day and into Wednesday.

E-mail teiserer@wfaa.com

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