LONDON  Assisted suicide has been illegal in England for nearly 50 years. But, ordered by the courts to clarify the law, the country’s top prosecutor on Wednesday set out a list of conditions under which his office would be unlikely to prosecute people who helped friends or relatives kill themselves.

The new guidelines are likely to make it easier for the terminally ill and those with degenerative diseases to receive help in committing suicide. But the prosecutor, Keir Starmer, the director of public prosecutions, appears to have waded into a legal and emotional thicket.

While there is little legislative appetite to make assisted suicide legal here, prosecutors have tended to interpret the existing law flexibly, quietly and case by case. The new guidelines are an attempt to codify their decision-making, but they have raised other issues, including questions about the role of doctors in assisted suicide, experts say.

In a statement, Mr. Starmer said that the law  under which “aiding, abetting, procuring or counseling” suicide is punishable by up to 14 years in prison  had not changed and that there were “no guarantees against prosecution.”