"Privity" has nothing to do with the art of building outdoor toilets or of pruning hedges into imaginative shapes. It is an old legal doctrine that has been successfully invoked by generations of defense lawyers to get all sorts of damage suits thrown out of court. If the plaintiff and the defendant had no direct contractural link, the defense lawyers would insist on a "lack of privity" as a bar to any legal action.

But the law is changing so quickly, opening up the courts to so many new kinds of suits, that a claim of lack of privity is fast becoming as rare as outhouses and greenery clipped to resemble swans. Recently, the District of Columbia Court of Appeals added Washington to the list of jurisdictions where the defense is much less useful.

In a traditional situation, if a woman went to her neighborhood hairdresser for a permanent, and a defect in the waving solution turned her locks Kelly green, she could not sue the maker of the lotion. Since she had had no dealings with the manufacturer, had given the company no money and not relied on any promise it made, she could not sue.

But developments in product liability law over the past decade make such suits much more routine now.

The newest development is an extension of this concept to contracts not for products, but for services. And it is the lawyers themselves who are feeling the heat.

Here's what happened in the case that evoked the D.C. Court of Appeals ruling two months ago: Elizabeth McC. Jones wanted to leave the residue of her estate--the property remaining after specific bequests were paid--to her nephew, Robert C. Needham. A number of versions of her will included that provision: it was the 13th paragraph of a version prepared in 1974. A few weeks later, Jones decided she wanted to leave some specific bequests to her grandnieces and grandnephews.

The lawyers wrote that intention in as a new paragraph 13. In having the will retyped, the old paragraph 13, naming Needham as the residuary heir, was inadvertantly dropped.

No one discovered the error until two days after Jones died in January 1980. With the will naming no one to inherit what remains in the estate, D.C. law takes over to decide how the property will be divided. And under those rules Needham gets only half. He sued the lawyers who drafted the will to collect the equivalent of the other half. But since the lawyers worked for Jones, not for Needham, Superior Court Judge Fred L. McIntyre found a lack of privity and dismissed the case.

But the appellate judges, admitting that such a case had never come before them, decided that the privity doctrine should no longer be stretched to ban such suits. (It is a good bet that the reason that such a case had never before gotten to the Court of Appeals is that until now the law was so settled in not allowing the action that no one had tried to bring one.)

It is obvious, the judges explained, that the whole idea of hiring someone to draft a will is to benefit the heirs; so those heirs should have a right to sue if a lawyer's negligence keeps them from getting what would otherwise be their rightful due.

The judges could point to a 60-year-old U.S. Supreme Court decision opening a hole in the privity doctrine in support of their position. But what is much more important is that in recent years courts in other states have also decided to let intended beneficiaries with claims that they suffered from poorly drafted wills sue the lawyers who drew up the documents, lack of privity not withstanding.

In Connecticut, New Mexico, Louisiana, Florida, and California there have been similar rulings. The initial California holding was even taken to the U.S. Supreme Court, but the justices declined to review the issue.

But the trend reaches well beyond questions of improperly written wills to all sorts of alleged legal malpractice. The National Tort Law Digests, a newsletter addressed to plaintiff lawyers, points to such cases as "newly developing opportunities." One recent example: the Illinois Supreme Court reinstated a case by children of a divorced woman, who claim that because their mother's lawyer failed to firmly lockup in the divorce decree their father's promise to continue them as beneficiaries of his insurance policy, they lost the proceeds to their father's second wife.

Judges, being lawyers themselves, have been more cautious about jettisoning the privity doctrine in malpractice cases than they were in product liability cases. "The attorney's obligation to his client must remain paramount," the Illinois justices explained in the divorce case. And so a lawyer trying to serve a client cannot be distracted by worries that someone, somewhere may come up with a vague claim that he or she was tangentially affected by poor advice given the client. But there were limits.

The judges are setting those limits where it is clear--and can be shown at trial--that the person who hired the lawyer specifically wanted to help someone else and that it is that someone else who is now suing. But that limitation still includes an awful lot of persons who may lack privity but who have a lot of interest in the quality of service provided by a professional. And a significant percentage of those persons are going to sue.