The Carlos Fierro defense team will face an uphill battle winning a new trial on the basis of erroneous instructions given to the jury, some experts say.

"It's clear the jury was extremely meticulous and thorough before it did agree unanimously on the verdict," said Mark Donatelli, a criminal defense lawyer. "If it had been only a few hours, it might have been a different story."

Errors in jury instructions are caught all the time after deliberations begin, Donatelli said, although he added, "I'm not aware of (a case) when the change was as significant as this one."

The error came to light after jurors questioned how much responsibility for the accident the defendant had to bear to be convicted of vehicular homicide.

The jury instructions submitted by the defense said the state had to prove the defendant was "the significant cause of the death of William Tenorio."

The uniform jury instructions, however, say the state must prove that "the defendant's act was a significant cause of the death."

Attorneys on either side of a case can submit their own jury instructions. "You can make up the most imaginative stuff you want," said retired Supreme Court Justice Paul Kennedy. "That's how it's done."

The instructions, however, must be supported by the law, with citations of applicable cases.

And, if either side submits instructions that differ from the "uniform jury instructions," that must be indicated on the "dirty copy," the document that is presented to the court. (A clean copy will ultimately be given to the jury.)

"They can tender any instructions they want. I do it all the time," said Tony Scarborough, a former Supreme Court justice. But, he added, "If you've made a modification, it must be noted. You can't run away from it by not noting it. If it doesn't contain the notation that it's been altered, it is misleading and deceptive."

In the Fierro case, the defense apparently noted that its proposed instructions had been altered. And, according to Kennedy, the defense supplied evidence that the standard of guilt proposed was the standard in 28 other states.

Normally, jury instructions are closely scrutinized by both sides. "Non-uniform jury instructions ordinarily receive additional scrutiny from opposing council. Both sides are looking at them to see if they are inaccurate, whether (they track) the language of the opinion (counsel) is relying on," Donatelli said.

That apparently didn't happen here.

"In this case, (District Attorney Angela "Spence") Pacheco accepted the defendant's packet of charging instructions without reading them. It is a serious mistake," Scarborough said.

Although the judge is ultimately responsible for correctly instructing the jury, judges normally defer to the attorneys in a case. "If they don't object, the judge doesn't go through and nitpick it. He counts on prosecutors and lawyers to bring (the problems) to him," Scarborough said.

Scarborough said he had never had an experience in which the state agrees with his instructions. "They come with their own packet and insist upon using it," he said.

But here the prosecution didn't present its own instruction and, "if you don't object, you waive," Kennedy said.

Another opportunity for correcting the mistake occurred when the instructions were read to the jury. No one objected at that time, Donatelli pointed out, even though in homicide law in New Mexico, "the Supreme Court has said over and over that the defendant's actions needs only to be a significant or substantial cause of death." He added, "It's surprising the prosecution wasn't alerted that something was wrong" at that time.

Uniform jury instructions, which are written by a committee of the state Supreme Court and have the same power as a court ruling, "are always in a state of being improved," said Trace Rabern, an appellate writer who has been blogging about the Fierro case and the challenges of a causation defense in a vehicular homicide case.

Ideally, she said, they should be written and hammered out prior to trial. But in practice, many judges prefer to wait until all the evidence is in.

"It's always a work in progress," Kennedy said. "It's critical to both sides and makes a big difference — a huge difference," as this case illustrates.

Contact Anne Constable at 986-3022 or aconstable@sfnewmexican.com.