Psalm. 58:3 "The wicked are estranged from the womb: they go astray as soon as they be born, speaking lies."
There are some that argue "a lie is a lie" no matter what the circumstances. Some say that we have to choose the lesser of two evils at times. Others allow for an ethical suspension of some sort depending on the context. For example, if the Gestapo comes to your door demanding that you give up the whereabouts of the Jews you are not obligated to tell them the truth of their whereabouts. Or as in the biblical record the Israelite women during Pharaoh's time did not allow the destruction of their progeny, but the midwives said "the women are quick to give birth." Though it has been argued that God increased the time of the birth process, I think that this is not necessarily the case as we see another account where Rahab the harlot was deceptive in hiding the men of Israel, and because of this she was esteemed as a woman of faith.
What is it that constitutes a lie? The philosopher Kant in his categorical imperative would argue that a lie is a lie no matter what the context. If it is wrong to tell a lie it is wrong--universally. Are there times when God suspends the ethical ramifications of a lie? I.e it is okay sometimes to tell a lie. Perhaps it is a "white" lie of some sort?
The answer is no. Consider this definition. A lie is to intentionally (or as an indirect consequence) mislead with the intention of doing harm. With this definition we can retain the integrity of "Thou shalt not bear false witness." Making god's moral law mutable when it is immutable is a major theological blunder.
With such a definition we can see that in a practical context it would not be wrong to misdirect the evil intentions of evildoers. We are not required to aid in their evil means to accomplish their evil ends. We would be partakers of their evil deeds.
To further illustrate my point. Consider the just war. We would be foolish to reveal our strategy to the enemy if the enemy implored us to do so based on the "condition" that we would be unethical to "lie." Furthermore we have everyday practical examples to consider. When playing a game such as hiding seek, poker, base ball, the reality show survivor, etc. we are not bound by God's law to "show our hand." Bluffing is allowed and should not be seen as unethical. When "horse trading" in business deals we are not being unethical by not revealing our bank statement.
And so it is that we are not made subject by the rules of deceivers to follow suit in their deception. Their means to an end is evil. God has the ability to use evil for good. We too are able to redirect evil means for good. God never requires us to choose evil even if it is the lesser of two evils; rather we are to choose the greatest possible good. There is no such thing as there being a time when it is ethical to lie. This is true both theologically and philosophically.