When DNA crime evidence is strong, prosecutors can attest that only one person out of as many as a billion is likely to have DNA matching that found at the crime scene.  This can make a persuasive case when combined with other evidence.  But are those odds correct?  Scientists said in the 1980s that the odds of two people having the same DNA profile were about 9 billion-to-1.  Today, the odds vary, depending on the expert.

Ronald Goodbread, a Washington, D.C. defense lawyer, says he’s heard experts cite probabilities ranging from 184 billion-to-1 to 3,000-to-1.  Because the figures are still disputed, Goodbread says the test is a questionable means of proving guilt beyond a doubt.  “Show me a system with that kind of margin of error, and I’ll show you a system I don’t want my life hanging on,” says Goodbread.

“This is an area in flux, and changes are made year to year or month to month,” says Mark Bloom, assistant director of the DNA learning center at New York’s Cold Spring Harbor Lab.  “People will flip-flop back again before DNA is used consistently in U.S. courts,” he says.  “If you inject DNA into a jury, the lay person says ‘Aha.  Super science.  Guilty.’  It’s light-years from that,” he says.

There have been major breakthroughs in the application of DNA testing in the conviction of offenders.  DNA testing was used for the first time in 1987 to secure a rape conviction in an Orlando, Florida court case.  Since then, DNA testing has been used in more than 24,000 American criminal cases.  In April of 1994, convicted murderer Timothy Spencer died in Virginia’s electric chair.  Spencer was the first person to be executed in a case based on DNA evidence. It is increasingly common to have DNA evidence presented in cases dealing with assault charges, particularly those of a sexual nature.

Prosecutors rarely hinge a case solely on DNA testing, says Rockne Harmon, deputy district attorney for Alameda County in Oakland, CA.  “It’s not like a fingerprint, but it has powers of its own when you need it.”  Both prosecutors and defense attorneys agree the technique can be flawless in excluding criminal suspects.  You don’t have to deal with statistical probabilities.  You either have a match or you don’t.  Out of 8,000 cases studied at the FBI lab, 35% of conclusive results eliminated the suspect.  Critics charge that prosecutors and the FBI claim more accuracy for the testing techniques than they warrant and they inflate probability figures to downplay the chances of a mismatch.

DNA evidence is especially useful in rape cases.  The FBI and Scotland Yard report that one-third of all suspects in rape cases are released before booking because DNA evidence exonerates them.  Until recently, few defense attorneys could refute the prosecutions’ complex calculations.  That left juries in awe of the apparent accuracy of DNA tests.  Most trials where genetic evidence is admitted end in conviction, and in only a handful of cases has the jury chosen to ignore DNA crime data.

In recent years, defense lawyers have grown more successful in attacking DNA profiling.  The debate has left appellate courts confused.  In most states, scientific evidence is admissible only when it has “gained general acceptance” in the scientific community.  That standard was recently overturned by the U.S. Supreme Court, giving judges more latitude in accepting such evidence.  California, however, still abides by the old restrictive standard, and at least one state appeals court has ruled DNA evidence inadmissible.

Within the decade, the faster PCR genetic test, coupled with more discriminating techniques, will require even less tissue and produce far more certain odds of a match.  Though DNA testing has been used in only a small fraction of rape and murder cases, juries are beginning to expect genetic evidence.

Pennsylvania’s Superior Court ruled in December of 1992 that every accused rapist in the state is entitled to DNA testing in an effort to prove innocence.  The ruling could force the state’s prosecutors to test DNA in all rape cases.  Today, most states allow DNA testing in court, even if its admissibility is not consistent from state to state.

The costs involved – both time and money – to prove a suspect’s guilt in court is a strong disadvantage of DNA fingerprinting’s use as conviction evidence.  Countless dollars have been spent on expert witnesses, not to mention lawyers, in a series of pretrial admissibility hearings around the country.  After weighing the competing claims of scientific experts, one court will find DNA crime evidence admissible, while the next court, often hearing from the same experts, will conclude just the opposite.

The crime of sexual assault is a compilation of several different acts that involve conduct of a sexual or indecent nature toward someone else that is accompanied by physical force or even the threat of physical force or that causes fear, shame, or mental suffering. The essential element in all sexual assaults is lack of consent. Basically, sexual assault can include any adult sexual activity and can be divided into two sub-categories; physical sexual assault and non-physical sexual assault.

Sexual assaults of a physical nature include severe acts such as: intercourse / rape (the forceful sexual penetration of another), spousal rape (a spouse or domestic partner who has had sexual relations with the perpetrator but in the specific instance did not wish to do so), sodomy, oral copulation (both of which are types of rape), hand to genitalia contact, date rape (a person agrees to meet or go somewhere with the perpetrator but does not want sexual contact) and the torture of a victim in a sexual manner. Physical acts that are less severe in nature include inappropriate touching (unwanted pinching, slaps on the buttocks), forced kissing and forced nudity, photography, and video of people in sexual poses against their will (the victim in this case is aware of what is taking place).

Sexual Assaults of a non physical nature are considered sexual assault but do not include the element of force but still lack the victims consent. Acts of this nature include groping in crowds, peeping, sexting (the act of sending sexually explicit messages or photos electronically, primarily between cell phones), statutory rape (sexual contact that occurs with a person who is a minor and thus cannot legally give consent) and contact between any body parts and the private parts of another. This last is termed as lewd and lascivious conduct which is a legal term for any other behavior that is intended to arouse sexual pleasure for the assailant. Lewd and lascivious conduct is a broad category of sexual assault used by law enforcement when exactly what happened is not clear. When the acts are not clearly defined, the lack of consent and the intent to arouse sexual gratification will be used as a test to determine if the behavior is a sexual assault. According to the National Crime Victimization Survey, sexual assault also includes verbal threats, for example “wait until I get you home I’m going to….” or “ you look so hot I am going to ….” etc.

Sexual assault charges and penalties vary due to the broad area that the crime covers. Factors that influence penalties includes; the state that you are charged in, whether it was aggravated (a weapon was involved) the age of the victim and the seriousness of the offense. Sexual assaults of a non physical nature will like mete out far less penalties than offenses that are of a forcible nature. Penalties range from misdemeanor charges (less than one year in the county jail, a fine or both) for something such as sexting or peeping. The greater physical such as date rape offenses carry more penalties and are generally classified as felonies. The penalties range from one year in state prison to life in prison for aggregated cases or repeat offenders. Typically the federal government prosecutes these crimes only if they involve the crossing of state lines, occur on federal property, or involve a minor under twelve. The penalties for federal crimes range from not less than one year to life in prison. All states currently have sex offender registration laws and the federal government requires that a person must register if they are convicted of felony sexual assault charges. This will follow the perpetrator throughout their life as registry is published on the internet and offenders must re-register if they move.

Defending sexual assault charges in the criminal justice system is difficult but can be done. In cases that do not involve a minor, consent can be challenged. Other defenses include entrapment, or false allegations. One study showed that over a 9-year period, up to 16% of sexual assault allegations in one center were shown after police investigation to be false allegations which is a crime.