Certainly there were several things that could have been done to accelerate the death of a crucifixion victim. One particularly brutal method, which the Jews recommended on this occasion, was the breaking of the victim's legs. Under normal circumstances, one would not die from having his legs broken. However, it has been suggested that one who is attached to a cross would have great difficulty breathing deeply if he were not able to raise himself up, ever so slightly, to inhale oxygen. Thus, breaking the legs of a crucifixion victim would cause them to die rapidly via asphyxiation. The hypocrisy of the Jews is again seen here (cf. Matt. 23:23). They weren't willing to ceremonially defile the Sabbath by leaving the bodies on the crosses overnight, yet they are willing to murder an innocent Man!
John 19:32-34 - "Then the soldiers came and broke the legs of the first and of the other who was crucified with Him. But when they came to Jesus and saw that He was already dead, they did not break His legs. But one of the soldiers pierced His side with a spear, and immediately blood and water came out." The legs of the two robbers were likely broken by using a large mallet (i.e., a first-century equivalent of a sledge-hammer), but there was no point in breaking the legs of a Man already deceased! Why did a soldier pierce Jesus' side? No doubt it was to insure that Jesus really was dead. Had Jesus still been alive, this would have finished Him off.
It should be noted that some unbelievers affirm that Jesus never really died on the cross (and thus, He was never raised from the dead). They suggest that Jesus swooned on the cross and that He later revived in the tomb. This ridiculous theory has numerous difficulties, the main one being that the Romans were no fools when it came to the executing process. These soldiers knew how to kill and they knew when they had successfully completed their task. Besides, how could Jesus have fooled everyone present into thinking that He was dead? How could He have revived after losing so much blood and without receiving medical attention? How could water and blood come from His side if He were still living? How could He have had any strength to move a large stone in His condition on early Sunday, especially since He hadn't eaten in days? How could He have convinced His disciples that He had conquered death if He was just hanging on to life by the skin of His teeth?
Many have speculated that this flow of blood and water suggests that Jesus died of a ruptured heart. Although this may be the case, such must be harmonized with the notion that Jesus died voluntarily ("He gave up His spirit" - John 19:30). Others believe this phenomenon resulted from the total and complete exhaustion that characterized Him in His last hours before death.
Commentators have made some interesting suggestions regarding possible symbolism in the flow of water and blood from Jesus' side. It is known that Jesus died for our sins, and His death provided a means of cleansing. However, under the terms of the gospel, sins are washed away by water (the physical element) and blood (the spiritual element). This happens when a penitent believer submits to Scriptural immersion (cf. Heb. 10:22; Acts 2:38; Rev. 1:5; Rom. 6:3,4). Some believe that since both of these fluids were seen by a faithful witness to flow from the side of our crucified Lord, this truth was being emphasized symbolically. However, it may simply be that John was testifying to the fact that Jesus, the Son of God, really did die as a Man on the cross, contrary to the false Gnostic notion that His "divine side" came at baptism and departed prior to Calvary (cf. I John 5:6,8).
Although there is much that can be speculated upon regarding this verse, there are several things we can know as facts pertaining to the shedding of Jesus' blood: We can know that justification is through His blood (cf. Rom. 5:9), the church was purchased with His blood (cf. Acts 20:28), and God made "peace through the blood of His cross" (Col. 1:20).