Due Process
The Due Process Clause of the Fourteenth Amendment provides that "no State shall ... deprive any person of life, liberty, or property without due process of law." Due process is the right to notice when the government makes a decision affecting your interests. It is also the right to have an opportunity to be heard, typically in a court of law, and argue that you were not treated fairly. However, due process is only required where a protected liberty (such as the right to privacy) or property interest (the right to keep your job under an employment contract) will be affected.
My son was brutally beaten by a police officer. What constitutional rights have been violated?
Your son's treatment violates his right to substantive due process. Every person has the right to be free from government actions (in this case, a police officer's) that are so severe and disproportionate to the need presented that the conduct is propelled by malice or sadism. Once excessive force is used, the police officer crossed the "constitutional" line.
The conduct has to be more than a merely careless or unwise excess of passion; it must amount to a brutal and inhumane abuse of official power that shocks the conscience. For example, a football coach who requires players to run laps in 100 degree weather probably is not violating their substantive due rights. However, the coach that drags a player by his or her hair down the hall of the school because he or she did not complete the laps is violating those rights.
A teacher grabbed my son and pushed him against the wall when my son refused to go to the cafeteria instead of detention hall. Have my son's substantive due process rights been violated?
No. The teacher's actions may fall within the "corporal punishment" exception to excessive force. Although corporal punishment can certainly be excessive, it is not automatically excessive. The teacher can argue that he applied force in good faith to maintain or restore discipline.
Numerous court opinions hold that a school official's actions, when done to maintain discipline, constitute corporal punishment rather than excessive force. However, a student has the right to be free from excessive corporal punishment.
TIP: The ability to use force depends on the situation. In the example above, there would not be a good faith application of force if the student had been a petite girl going to a class, rather than detention hall.