Suspects in UK student’s death had undeveloped brains, expert says

Lexington police arrested Efrain Diaz, left, and Justin Smith, 18, right, both of Lexington, in 2015 on charges of murder in the killing of University of Kentucky student Jonathan Krueger.
Lexington police arrested Efrain Diaz, left, and Justin Smith, 18, right, both of Lexington, in 2015 on charges of murder in the killing of University of Kentucky student Jonathan Krueger.

A judge heard testimony Monday in support of a motion to exclude the death penalty in the case of two co-defendants charged in the 2015 slaying of University of Kentucky student Jonathan Krueger.

Efrain Diaz, 22, and Justin Delone Smith, 20, seek to avoid the death penalty by arguing that their young brains weren’t fully developed during the robbery and shooting of Krueger, 22, on East Maxwell Street near the UK campus. At the time, Diaz was 20 and Smith was 18.

In 2005, the U.S. Supreme Court ruled that defendants can’t be executed for crimes they committed when they were younger than 18. A third defendant charged with Krueger’s murder, Roman Gonzalez, who was 17 at the time, already is protected by that Supreme Court ruling and faces a maximum penalty of life in prison.

Laurence Steinberg, professor of psychology at Temple University in Philadelphia, testified Monday that research since 2005 has shown that human brains don’t fully mature until the mid-20s. Steinberg helped draft an American Psychological Association brief for the case in which the Supreme Court outlawed the death penalty for crimes committed before age 18.

“In the last 10 years or so, we have seen that a lot of the maturation that takes place between the ages 10 and 18 is actually ongoing into the early 20s and up until, we think, the mid-20s,” Steinberg said. “That is now well established in the scientific literature.”

Justice Anthony Kennedy stated in his 2005 majority opinion that the difference between offenders younger than 18 and adults is that juveniles are impetuous, that they are susceptible to negative outside influences such as peer pressure, and that their character is not as well formed as adults.

“Based upon your studies, do those characteristics apply to 20-year-olds?” public defender Michael Bufkin asked.

“Yes, they do,” Steinberg said.

Commonwealth’s Attorney Lou Anna Red Corn asked Steinberg whether a person at age 18 knows the difference between right and wrong.

“Absolutely,” Steinberg said.

“Using your understanding of the science as you’ve represented it to us,” Red Corn asked, “should we change the age of maturity in making decisions about getting married to 21? Should they have to be 21 and older to get married?”

“I wouldn’t change it for getting married,” Steinberg said.

“What about driving a car?” Red Corn asked.

“I think the driving age should be raised,” Steinberg said. “I think it should be raised to at least 18.”

Steinberg said later that he would be hesitant about drawing parallels between the minimum age for death-penalty eligibility and the minimum age for marriage, driving privileges and making one’s own medical decisions.

“You can drive at 16, but you can’t see an X-rated movie at that age,” Steinberg said. “You can vote at 18, but you can’t buy alcohol at that age.”

During cross-examination, Steinberg acknowledged that he is personally opposed to the death penalty.

Steinberg also said that he is being paid for his testimony, and that his rate is $500 an hour. He couldn’t immediately calculate his bill, but he said it is to be no more than $10,000 for his preparation, travel and testimony for Monday’s hearing.

Fayette Circuit Judge Ernesto Scorsone made no decision after the hourlong hearing. Scorsone said he would like to see the research since 2005 in regard to brain development.

Diaz, Gonzalez and Smith are scheduled to go on trial in October. The trial is expected to take four weeks.