There was a time in the United States when your business was also your boss's business. At the turn of the century, company snooping was pervasive and privacy almost nonexistent. Your boss had the right to know who you lived with, what you drank, whether you went to church, or to what political groups you belonged. With the growth of the trade union movement and heightened awareness of the importance of individual rights, American workers came to insist that life off the job was their private affair not to be scrutinized by employers.

But major chinks have begun to appear in the wall that has separated life on and off the job, largely due to the advent of new technologies that make it possible for employers to monitor their employees' off-duty activities. Today, millions of American workers every year, in both the public and private sectors, are subjected to urinalysis drug tests as a condition for getting or keeping a job.

The American Civil Liberties Union opposes indiscriminate urine testing because the process is both unfair and unnecessary. It is unfair to force workers who are not even suspected of using drugs, and whose job performance is satisfactory, to "prove" their innocence through a degrading and uncertain procedure that violates personal privacy. Such tests are unnecessary because they cannot detect impairment and, thus, in no way enhance an employer's ability to evaluate or predict job performance.

Here are the ACLU's answers to some questions frequently asked by the public about drug testing in the workplace.

Q: Don't employers have the right to expect their employees not to be high on drugs on the job?

A: Of course they do. Employers have the right to expect their employees not to be high, stoned, drunk, or asleep. Job performance is the bottom line: If you cannot do the work, employers have a legitimate reason for firing you. But urine tests do not measure job performance. Even a confirmed "positive" provides no evidence of present intoxication or impairment; it merely indicates that a person may have taken a drug at some time in the past.

Q: Can urine tests determine precisely when a particular drug was used?

A: No. Urine tests cannot determine when a drug was used. They can only detect the "metabolites," or inactive leftover traces of previously ingested substances. For example, an employee who smokes marijuana on a Saturday night may test positive the following Wednesday, long after the drug has ceased to have any effect. In that case, what the employee did on Saturday has nothing to do with his or her fitness to work on Wednesday. At the same time, a worker can snort cocaine on the way to work and test negative that same morning. That is because the cocaine has not yet been metabolized and will, therefore, not show up in the person's urine.

Q: If you don't use drugs, you have nothing to hide -- so why object to testing?

A: Innocent people do have something to hide: their private life. The "right to be left alone" is, in the words of the late Supreme Court Justice Louis Brandeis, "the most comprehensive of rights and the right most valued by civilized men."

Analysis of a person's urine can disclose many details about that person's private life other than drug use. It can tell an employer whether an employee or job applicant is being treated for a heart condition, depression, epilepsy or diabetes. It can also reveal whether an employee is pregnant.

Q: Are drug tests reliable?

A: No, the drug screens used by most companies are not reliable. These tests yield false positive results at least 10 percent, and possibly as much as 30 percent, of the time. Experts concede that the tests are unreliable. At a recent conference, 120 forensic scientists, including some who worked for manufacturers of drug tests, were asked, "Is there anybody who would submit urine for drug testing if his career, reputation, freedom or livelihood depended on it?" Not a single hand was raised.

Although more accurate tests are available, they are expensive and infrequently used. And even the more accurate tests can yield inaccurate results due to laboratory error. A survey by the National Institute of Drug Abuse, a government agency, found that 20 percent of the labs surveyed mistakenly reported the presence of illegal drugs in drug-free urine samples. Unreliability also stems from the tendency of drug screens to confuse similar chemical compounds. For example, codeine and Vicks Formula 44-M have been known to produce positive results for heroin, Advil for marijuana, and Nyquil for amphetamines.

Q: Still, isn't universal testing the best way to catch drug users?

A: Such testing may be the easiest way to identify drug users, but it is also by far the most un-American. Americans have traditionally believed that general searches of innocent people are unfair. This tradition began in colonial times, when King George's soldiers searched everyone indiscriminately in order to uncover those few people who were committing offenses against the Crown. Early Americans deeply hated these general searches, which were a leading cause of the Revolution.

After the Revolution, when memories of the experience with warrantless searches were still fresh, the Fourth Amendment was adopted. It says that the government cannot search everyone to find the few who might be guilty of an offense. The government must have good reason to suspect a particular person before subjecting him or her to intrusive body searches. These longstanding principles of fairness should also apply to the private sector, even though the Fourth Amendment only applies to government action.

Urine tests are body searches, and they are an unprecedented invasion of privacy. The standard practice, in administering such tests, is to require employees to urinate in the presence of a witness to guard against specimen tampering. In the words of one judge, that is "an experience which even if courteously supervised can be humiliating and degrading." Noted a federal judge, as he invalidated a drug-testing program for municipal fire-fighters, "Drug testing is a form of surveillance, albeit a technological one."

Q: But shouldn't exceptions be made for certain workers, such as airline pilots, who are responsible for the lives of others?

A: Obviously, people who are responsible for others' lives should be held to high standards of job performance. But urine testing will not help employers do that because it does not detect impairment.

If employers in transportation and other industries are really concerned about the public's safety, they should abandon imperfect urine testing and test performance instead. Computer-assisted performance tests already exist and, in fact, have been used by NASA for years on astronauts and test pilots. These tests can actually measure hand-eye coordination and response time, do not invade people's privacy, and can improve safety far better than drug tests can.

Q: Drug use costs industry millions in lost worker productivity each year. Don't employers have a right to test as a way of protecting their investment?

A: Actually, there are no clear estimates about the economic costs to industry resulting from drug use by workers. Proponents of drug testing claim the costs are high, but they have been hard pressed to translate that claim into real figures. And some who make such claims are manufacturers of drug tests, who obviously stand to profit from industry-wide urinalysis. In any event, employers have better ways to maintain high productivity, as well as to identify and help employees with drug problems. Competent supervision, professional counseling and voluntary rehabilitation programs may not be as simple as a drug test, but they are a better investment in America.

Our nation's experience with cigarette smoking is a good example of what education and voluntary rehabilitation can accomplish. Since 1965, the proportion of Americans who smoke cigarettes has gone down from 43 percent to 32 percent. This dramatic decrease was a consequence of public education and the availability of treatment on demand. Unfortunately, instead of adequately funding drug clinics and educational programs, the government has cut these services so that substance abusers sometimes have to wait for months before receiving treatment.

Q: Have any courts ruled that mandatory urine testing of government employees is a violation of the Constitution?

A: Yes. Many state and federal courts have ruled that testing programs in public workplaces are unconstitutional if they are not based on some kind of individualized suspicion. Throughout the country, courts have struck down programs that randomly tested police officers, fire-fighters, teachers, civilian army employees, prison guards and employees of many federal agencies. The ACLU and public employee unions have represented most of these victorious workers.

In Washington, D.C., for example, one federal judge had this to say about a random drug testing program that would affect thousands of government employees: "This case presents for judicial consideration a wholesale deprivation of the most fundamental privacy rights of thousands upon thousands of loyal, law-abiding citizens...."

In 1989, for the first time, the U. S. Supreme Court ruled on the constitutionality of testing government employees not actually suspected of drug use. In two cases involving U. S. Customs guards and railroad workers, the majority of the Court held that urine tests are searches, but that these particular employees could be tested without being suspected drug users on the grounds that their Fourth Amendment right to privacy was outweighed by the government's interest in maintaining a drug-free workplace.

Although these decisions represent a serious setback, the Court's ruling does not affect all government workers, and the fight over the constitutionality of testing is far from over.

Q: If the Constitution can't help them, how can private employees protect themselves against drug testing?

A: Court challenges to drug testing programs in private workplaces are underway throughout the country. These lawsuits involve state constitutional and statutory laws rather than federal constitutional law. Some are based on common law actions that charge specific, intentional injuries; others are breach of contract claims. Some have been successful, while others have failed. Traditionally, employers in the private sector have extremely broad discretion in personnel matters.

In most states, private sector employees have virtually no protection against drug testing's intrusion on their privacy, unless they belong to a union that has negotiated the prohibition or restriction of workplace testing. One exception to this bleak picture is California, in which the state constitution specifies a right to privacy that applies, not only to government action, but to actions by private business as well.

In addition to California, seven states have enacted protective legislation that restricts drug testing in the private workplace and gives employees some measure of protection from unfair and unreliable testing: Montana, Iowa, Vermont and Rhode Island have banned all random or blanket drug testing of employees (that is, testing without probable cause or reasonable suspicion), and Minnesota, Maine and Connecticut permit random testing only of employees in "safety sensitive" positions. The laws in these states also mandate confirmatory testing, use of certified laboratories, confidentiality of test results and other procedural protections. While they are not perfect, these new laws place significant limits on employers' otherwise unfettered authority to test and give employees the power to resist unwarranted invasions of privacy.

The ACLU will continue to press other states to pass similar statutes and to lobby the U.S. Congress to do the same.

A.C.L.U. American Civil Liberties Union, 132 West 43rd Street, NY, NY 10036