(CBS) Wuterich says he also didn't fire his weapon in the second house.

In that second house was the Younis family. A 41-year-old man, a 35-year-old woman, a 28-year-old woman, and the children -- Noor, 14; Sabah, 9; Zaineb, 3; and Aisha, 2. They were all killed by Wuterich's men.

How does he explain that?

"We reacted to how we were supposed to react to our training and I did that to the best of my ability. You know the rest of the Marines that were there, they did their job properly as well. Did we know that civilians were in there? No. Did we go in those rooms, you know, it would have been one thing, if we went in those rooms and looked at everyone and shot them. You know, we cleared these houses the way they were supposed to be cleared," he says.

Prosecutors have charged Wuterich with murdering 18 people. Among them the people at the car and those in the first house when he ordered his men to “shoot first, ask questions later.” Prosecutors say he shot six people in the second house. Wuterich told 60 Minutes that he never fired his weapon. The rules said Wuterich and his Marines were supposed to identify a threat before firing, but the rules also said they could use all necessary force to defend themselves.

"In an insurgency situation, Marines don't get a second chance If they aren't able to fire first, they die," says Neil Puckett, who, along with Mark Zaid, are Wuterich’s civilian attorneys.

How can they make the argument that these killings are within the law?

"They're within the law because they were not done without legal justification or excuse," Puckett says. "They were done in a combat environment, in a tactical situation, in order to protect the lives of the remaining Marines who survived the IED that day. And that makes them lawful."

Zaid adds: "And these three one Marines knew -- their buddies and colleagues who had tried to do similar take downs of houses where they tried, in fact, to knock first and shoot later. And the Marines who tried that were dead."

60 Minutes wanted to know more about how Marines face this choice - between killing civilians or risking their men. We spoke to a Marine who led a platoon through some of the most hostile territory in Iraq. Donovan Campbell, now a Reserve Captain, estimates he cleared at least 50 houses.

"We have a saying: 'Always know your target and what’s beyond it. And no matter what, whether you think you’re probably going kill everyone inside, you still need to know exactly what your target is. 'Who is it that I’m shooting when I go through the door,'" Campbell says.

Campbell was not in Haditha and he makes no judgment about what the Marines did there. But he told 60 Minutes, in general, identifying the enemy is critical and has everything to do with the amount of force used to clear a house.

Are there circumstances under which you’d declare an entire house hostile and go in with the intention of just killing everyone inside?

Campbell says yes. "You have to have the context of heavy enemy involvement in the area and then I think you have to have a more specific operating context that deals specifically with that house. You know there are several insurgents inside and you need to go in and get them out because they are attacking you."

How does one know? Campbell tells Pelley almost always, you have to see them.

"In your opinion," asks Pelley," you have to lay eyes on someone with a weapon in that house in order to assault the house and kill everyone inside?”

Campbell says, "Yes, but you never go in with the intention of I’m going to kill every living soul inside."

Produced by Shawn Efran and Solly Granatstein
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