Homicide
First-degree murder (or murder in the first degree, or colloquially, murder one) refers to: premeditated murder, or murder which occurs after some degree of reflection by the murderer. This reflection can be years or less than a second.
Second-degree murder refers to: murder done with malice but without premeditation.
Felony murder occurs: when a person is involved in a felony and someone dies during the course of committing a felony. This applies even if one does not personally or directly cause the person's death. For example, a getaway driver for an armed robbery can be convicted of murder if one of the robbers killed someone -- or got killed in the process of the robbery, even though the driver was not present at and did not expect the killing
Manslaughter is defined as the unlawful killing of another person without premeditation or so-called "malice aforethought" (an evil intent prior to the killing). It is distinguished from murder by lack of any prior intention to kill anyone or create a deadly situation.
There are two levels of manslaughter: voluntary and involuntary.
Involuntary manslaughter generally occurs in only two cases. The first is when someone is killed due to criminal negligence or recklessness. One example is when someone kills another because of drunk driving. Voluntary manslaughter occurs when a person intentionally kills another person after "adequate provocation"; that is, there has been action that was sufficient to incite an "ordinary person" to "sudden and intense passion" such that s/he loses self control. This usually occur in the heat of passion

CAUSES/EXPLANATIONS OF HOMICIDE
Physical/Physiological
Genetics
This explanation focuses on high incidence of XYY chromosome abnormality in males (that is those born with an extra Y chromosome). The XYY factor is felt by some scientists to be a relevant aspect of the total pattern that leads to aggressive behavior. Studies have shown that individuals with an extra Y chromosome are at considerably higher than average risk for being aggressive.

Organic
This includes tumor and head injuries. The potentially most dangerous symptom of organic disease is uncontrollable rage followed by unpredictable attacks precipitated by trivial provocation; some of these attacks are preceded by a period of increased anxiety and tension that are obvious to others.

Psychological
Psychoanalytic
Murderous impulses are believed to occur when there is a basic weakness of the ego or when the function is impaired by fatigue, physical illness, alcohol and drugs. In addition, there could be a malfunction of the superego caused by prolonged separation from the mother, unloving parents, criminal parents and a great deprivation during the first years of life. Surrounded by these circumstances, young people do not learn to control their pent up hostility and aggression. This can result in violence.

Social Learning (Media)
Murder is prime time interest for the public. Studies have shown that prolonged exposure to murder conditions some people to become insensitive to violent acts. Young people are particularly susceptible to this, because they imitate what they see on television.

Sociological
Environmental Factors
Bad housing, poor family life, inadequate community resources are related to crime. Crowding millions of people, with disadvantages, into urban ghettos not only offers the opportunity for violence but may also cause it.

Differential Association
Some people learn to be violence through close association with significant other; the family. The gang is a good example which teaches it members not only to skills, techniques but also the rationalizations for killing someone

Types of Serial Killers Based on Psychological Profile
Visionary
This type of serial killer almost always suffers from psychoses. They kill at the command of hallucinated voices. Instructions they receive justify and legitimize the act of