The Three Tier Test: 

Levels of Analysis for Equal Protection

STRICT SCRUTINY:  The government must show that the challenged classification serves a compelling state interest and that the classification is necessary to serve that interest.

A. Suspect Classifications:

Race

National Origin

Religion

Ethnicity

Alienage

B. Classifications Burdening Fundamental Rights

1. Denial or Dilution of the Vote

2. Interstate Migration

3. Access to the Courts

4. Other Rights Recognized as Fundamental (eg., "privacy")

HEIGHTENED SCRUTINY:  The government must show that the challenged classification serves an important state interest and that the classification is at least substantially related to serving that interest.

1.  Gender

2.  Illegitimacy

MINIMUM SCRUTINY:  RATIONAL BASIS TEST:   The govenment need only show that the challenged classification is rationally related to serving a legitimate state interest. Minimum scrutiny applies to all classifications other than those listed above (such as business regulations, public safety measures, taxes, etc.)   although some Supreme Court cases suggest a slightly closer scrutiny ("a second-order rational basis test") involving some weighing of the state's interest may be applied in cases, for example, involving classifications that disadvantage mentally retarded people, homosexuals, or innocent children of illegal aliens.

See Also:  Levels of Scrutiny Under the Equal Protection Clause

                 Craig v. Boren (1976)