Is it ever acceptable to take a human life? The Bible clearly commands, "Do not kill" (Exodus 20:13). But it also teaches exceptions to this rule. There are four exceptions.
The first is as a punishment for certain capital crimes (Genesis 9:6, Romans 13:4). God chose not to execute Cain for his murder of Abel, but He tells Noah later that killers should be killed by the human race. The Law of Moses expands greatly on this, set in the context of their theocracy. Man-stealing, for example, was a death-penalty crime (Exodus 21:16), which means that the entire North American slave trade was under a death-penalty judgment from God. A human life can be taken as a punishment for certain crimes, but the bar of proof is set high -- 2-3 eye-witnesses.
The second exception is to maintain civil order. In Exodus 32, God authorized the Levite tribe to use force to put down a massive riot going on among the people of Israel. This chaotic incident was the inspiration for the famous old hymn, "Who Is On The Lord's Side?", and began God's ordination of the Levite tribe as the priests of Israel. This was a reward from God, which means He approved of their actions. (Exodus 32:26-29). This did not mean, however, that the Levites could do whatever they liked and get away with it.
The third exception is in defense of innocent life. Jesus authorized his disciples to carry weapons (Luke 22), whose lawful use would be for self-defense. Christ chose not to defend Himself on the night of His betrayal because that was redemption's fulfillment. But He said He could have done so, if He had chosen (Matthew 26:53).
The last exception is as part of a lawful war, conducted lawfully. God Himself many times in the Old Testament authorized war by the Israelites against God's enemies. If war was innately evil, God would not and could not have done this because God cannot sin. Many wars are evil. Wars of plunder and land-grabbing are forbidden, for example (see Amos 1). And even in war, God had rules of engagement. The Lord condemned Joab for his vengeful killing of Abner while they met under the white flag of truce (2 Samuel 3).
Four exceptions, and no more. Under these rules abortions other than to save the life of the mother are forbidden, but so is police brutality. The Bible doesn't teach pacifism, but it condemns war-mongering and man-stealing just as clearly. Perhaps if we evangelicals paid more careful attention to the testimony of the Old Testament, we wouldn't be as confused on legal, social, and ethical issues as we sometimes seem to be.