The prosection in the trial of Ford Motor Co. on charges of reckless homicide received a severe blow today when the judge refused to allow into evidence potentially explosive company documents that balanced the cost of a design change against the value of a human life.

In the documents, a Ford official estimated that an $11 improvement in the fuel tanks of 12.5 million Ford cars and trucks could save an estimated 180 lives. But the official said the total cost of the change outweighed the benefits in saving human life. The documents put a $200,000 price on each life lost.

The documents also recommended a delay in any improvements until they were mandated by future federal safety standards.

Pulaski County Judge Harold Staffeldt ruled that the documents were "pretty far remote from the issue," which he said was whether a defect existed in the 1973 Pinto fuel tank.

A year ago an Indiana grand jury charged Ford with reckless homicide in the August 1978 deaths of three young women whose 1973 Pinto sedan was hit from behind by a van. The state alleges that Ford knew Pinto gasoline tanks were defective -- that they were prone to catch fire during rear-end collisions -- but it failed to warn the public or fix the problem.

The case represents the first time that a corporation has faced criminal charges stemming from its design of a product.

Today's arguments took place out of the prsence of the seven-man, five-woman jury.

Staffeldt ruled in the prosecution's favor on an equally crucial motion.

Ford sought a ruling preventing local prosecutors from alleging that federal safety standards governing the Pinto are inadequate. This allegation is central to the prosecution's case. Ford argued that it should be immune from criminal prosecution for the alleged safety defects because the car met federal safety standards at the time of production.

Ford attorney James Neal argued that to allow a state jury to decide that an auto maker has to adhere to tougher safety standards than those set by federal automobile regulators would be a "horrendous proposition."

"What we have," Neal argued, "is the total destruction of the automobile industry." He said that, under the prosecution argument, auto engineers could design a car that met federal safety standards at the time, only to find out later that some state jury decided the car should have been made safer.

Federal standards say that auto fuel tank systems must be able to withstand a 30 mph rear-end collision.Under the prosecution argument, Neal said, "some jury could say that an acceptable standard is really 70 miles per hour."

"I see absolute disaster if the prosecution is allowed to say the standard should be something more than 30 mph," he said.

The prosecution countered by saying that there was no regulation governing fuel system safety during rear-end collisions until the 1977 model year, four years after the 1973 Pinto involved in the case was built and sold.

Prosecution lawyer Bruce Berner said the same federal agency that sets safety standards, the National Highway Traffic Safety Administration, "found the 1973 Pinto [fuel system] defective, and issued a recall."

Federal standards are minimum standards, Berner argued. He cited several civil cases in which courts had ruled that existing federal standards did not preempt juries from setting their own acceptable levels of safety.

The prosecution said it will prove that Ford knew in 1973 that its Pinto fuel tank design was unsafe, but failed to warn owners or fix the cars.

Neal told reporters that the ruling on the federal standard issue represented a "bad omen" for American industry. Later, chief prosecutor Michael A. Cosentino said he was happy with that ruling, but added that his case would be hampered by Staffeldt's ruling on the cost-benefit information.

"I'd have to say it was a draw," Consentino said.

For the most part, the judge issued deliberately vague rulings on a dozen other defense motions seeking to limit evidence, leaving the door open for the introduction of certain documents "if the proper foundation is laid."

Many of the motions involve Ford documents on other than 1973-model Pintos, or other Ford cars. Staffeldt said those documents could be introduced if it was shown that they have some connection with the design or manufacture of the 1973 Pinto involved in the crash, or with Ford's later knowledge about problems with that car.

In one instance the court ruled as inadmissible information from civil trials involving Pintos.

The debate over documents became heated at times, with defense attorney Malcolm Wheeler accusing prosecutor Cosentino of "false" statements about the contents of the Ford memos.

Cosentino leaped to his feet and bellowed, "I'm not in the habit of being called a liar."

Earlier, Wheeler accused Cosentino of playing to the press when vividly describing the documents.

Opening arugments are scheduled for Tuesday afternoon, following discussion of a defense motion to prevent the prosecution from introducing reportedly gruesome photos of the crash victims.