How does Briggs call Osvaldos credibility into question

Brigg's questioning reveals that Cruz is testifying in return for a deal from the government.

O'Brien's questioning reveals Cruz's lie about his involvement in a gang.

PETROCELLI: Mr. Cruz, you’re testifying against people you know. Are you testifying because you’re getting a deal from the government?

OSVALDO: Yeah.

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BRIGGS: Well, I’m certainly glad you’re telling the truth, Mr. Cruz. But let me ask you, Mr. Cruz, hasn’t the prosecutor given you a choice? You go to jail or you put somebody else in jail? Isn’t that your choice?
OSVALDO: I don’t go around lying to people. Especially when I swear.
BRIGGS: And you did swear today, isn’t that correct? And it wouldn’t be right to lie under oath?
OSVALDO: Right.
BRIGGS: It wouldn’t be right to lie under oath, but it would be just fine to go into a drugstore and stick it up? That’s cool, isn’t it?