42 U.S.C. § 1983 provides in relevant part that:

Every person who, under color of any statute, ordinance, regulation, custom or usage of any State . . . subjects or causes to be subjected, any citizen of the United States . . . to the deprivation of any rights, privileges, or immunities secured by the Constitution and laws, shall be liable to the party injured in an action at law . . .

The purpose of § 1983 is to deter state actors from using the badge of their authority to deprive individuals of their federally guaranteed rights and to provide relief to victims if such deterrence fails.   State law also allows for recovery under alternate theories.  In California, a claim must be filed with the appropriate entity/agency within 6 months of the incident.  This time limitation is strictly enforced, but there are certain exceptions.

To succeed in a claim of a § 1983 violation, the burden is upon you (the plaintiff) to establish by a preponderance of the evidence that: (1) the defendant performed an act or acts which operated to deprive you of one or more of your Federal Constitutional rights; (2) the defendant acted under color of law; and (3) the defendant's acts were the legal cause of the damages sustained by the plaintiff.  
It is not necessary for a plaintiff to prove a defendant had the specific intent to deprive you of your  constitutional rights.

EXCESSIVE FORCE

The use of force is contrary to the Fourth Amendment if it is excessive under objective standards of reasonableness.  The use of force by officers is not reasonable under the Fourth Amendment is there is no need for force.
 
In determining whether the force used was reasonable, a court must balance the nature and quality of the intrusion on the individual's Fourth Amendment interests against the countervailing governmental interests at stake.

It is a question of fact as to what force a reasonable officer would have used which controls, not the state of mind of the defendant himself.  Evil intentions will not establish a constitutional violation if the force used was objectively reasonable, nor will good faith protect an officer who used unreasonable force.  The physical force must be objectively reasonable from the perspective of a reasonable police officer on the scene, not with the 20/20 vision of hindsight.

A claim of excessive force must be analyzed independently from a claim of false arrest. 
There are clearly established rules relating to excessive force claims:  The first factor in determining whether the force used was excessive is the severity of the force applied. The second factor, and the most important, is the need for the force. The amount of force used is  'permissible only when a strong government interest compels the employment of such force.'   Factors to be considered in determining the need for the force include  'the severity of the crime at issue, whether the suspect poses an immediate threat to the safety of the officers or others, and whether he is actively resisting arrest or attempting to evade arrest by flight.'  Finally, a court must balance the force used against the need, to determine whether the force used was greater than is reasonable under the circumstances. This determination requires careful attention to the facts and circumstances of each particular case and a careful balancing of an individual's liberty with the government's interest in the application of force.

Court have found excessive force in many varied circumstances. 

BATTERY

Pursuant to California Penal Code § 835(a), a police officer may use reasonable force to make an arrest, prevent escape or overcome resistance, and need not desist in the face of resistance.
 
To establish a battery claim against an officer in California, a plaintiff must prove facts which show unnecessary force was used. The rule in California is the same as that in federal excessive force cases under § 1983.

DETENTION

The Fourth Amendment protects a person from unreasonable searches and seizures.  The improper seizure of a person on a street will violate the Fourth Amendment. Whenver a police officer accosts an individual and restrains his freedom to walk away, he has 'seized' the person. A seizure for the purposes of the Fourth Amendment occurs when taking into account all the circumstances surrounding the encounter, the police conduct would have communicated to a reasonable person that he was not at liberty to ignore the police presence and go about his business.

The Fourth Amendment prohibits only (objectively) unreasonable seizures and the reasonableness of a seizure is measured by the totality of the circumstances. The way in which a seizure is effectuated can also render it unreasonable.

An arrest or detention without a judicial warrant is presumed unlawful and in violation of the Fourth Amendment.  Once a plaintiff meets this burden, the burden of proof shifts to the defendant(s) to establish either that (1) the detention was fbased upon articulable suspicion or (2) the arrest was based upon probable cause.  

The basic detention between a detention and an arrest is that in the case of a detention, it is likely (but not guaranteed) that you will be released once the police finish their investigation.  If further evidence is located in the course of the investigation, you will likely be arrested. 

A detention may not be premised on mere curiosity, rumor, or hunch that the detainee is involved in criminal activity. Instead, a detention must be justified by specific and articulable facts, measured by facts known to the officer at the time he detains the suspect.
 
It is well established that it is reasonable for an officer to temporarily display force or restrain a person until that person's relationship to the suspect and possible reaction to the situation can be ascertained.

A determination of whether an officer had reasonable suspicion or probable cause is not readily reduced to 'a neat set of legal rules.'  Rather, the court must consider the totality of the circumstances.  This includes the 'collective knowledge of the officers involved, and the inferences reached by experienced, trained officers.'   However, this experience may not be used to give the officers unbridled discretion in making a detention.

A detention may also be justified because a search warrant implicitly carries with it the limited authority to detain the occupants of the premises while the search is conducted.

FALSE IMPRISONMENT

False arrest or false imprisonment is the unlawful violation of the personal liberty of another.  (false arrest is but one way of committing a false imprisonment, and they are distinguishable only in terminology). 

All that is necessary to make out a charge of false imprisonment is that the individual be restrained of his liberty without any sufficient complaint or authority therefor . . . ..

INTENTIONAL INFLICTION OF EMOTIONAL DISTRESS
 
The elements of intentional infliction of emotional distress are (1) extreme and outrageous conduct by the defendant with the intention of causing, or reckless disregard of the probability of causing, emotional distress; (2) the plaintiff's suffering severe or extreme emotional distress; and (3) actual and proximate causation of the emotional distress by the defendant's outrageous conduct.'

In order to be considered outrageous, the conduct must be so extreme as to exceed all bounds of that usually tolerated in a civilized community.  The extreme and outrageous character of the conduct may arise from the abuse by the actor of a position, or a relation with the other, which gives him actual or apparent authority over the other, or power to affect his interests. 

QUALIFIED IMMUNITY

The United States Supreme Court has recognized qualified immunity for government officials where it [is] necessary to preserve their ability to serve the public good . . . . Police officers are one class of government officials entitled to qualified immunity.
 
The United States Supreme Court has established a two part analysis for determining the propriety of qualified immunity in a suit against an officer.   First, a court must consider whether the facts alleged show that the officer's conduct violated a constitutional right. In so considering, the court must view the alleged facts in the light most favorable to the party asserting injury. Second, and assuming a constitutional violation can be made from the facts, the court must determine whether the constitutional right was clearly established in light of the specific context of the case. The relevant, dispositive inquiry in determining whether a right is clearly established is whether it would be clear to a reasonable officer that his conduct was unlawful in the situation he confronted.

A police officer is not entitled to qualified immunity simply because there is no prior case prohibiting the use of this specific type of force in precisely the circumstances involved. 

It must be sufficiently clear to the officers that, acting  as a "reasonable officer" that their conduct was unlawful in the situation they confronted.