Yes, as a Christian, your word should be sufficient without having to say "I swear to God", "I cross my heart and hope to die", or put your hand on the Bible.
Jesus also talked about how anything beyond simply letting your yes be yes and your no be no comes from the evil one. Matthew 5:37
Thus, technically God's desires should be held higher even than those of our governing authorities. We are to submit to them except where they are in conflict with God's requests, so it would be the "most" correct thing in a court of law where they asked you to swear if you quickly referenced this truth from God and your strong conviction thereto as a believer and simply gave your word that you would not lie, which should be sufficient.
I haven't ever seen anyone with enough courage to do this, but it would be very refreshing.
Also, I'm not sure if the "condemned" the scripture is talking about is by "man" or by "God". People who are constantly swearing that they are telling the truth tend to lose credibility as you wonder why they feel the need to swear if they are sooo trustworthy. Thus, a defendant in a court of law who continued making comments about swearing that it happened the way he said would likely lose enough credibility with a jury to be "condemned".