State and federal courts have recognized that individuals acting in a legislative capacity are immune from liability for those actions. The legislative immunity doctrine is deeply embedded in Anglo American law, serving to encourage free and open debate.

The legislative immunity doctrine is not intended to protect individual legislators, but instead serves the public's interests. Because the immunity doctrine serves important public purposes, courts have affirmed that the doctrine generally shields legislative actors not only from liability, but also from being required to testify about their legislative activities.

The threat of liability can create perverse incentives that operate to inhibit officials in the proper performance of their duties. In many contexts, government officials are expected to make decisions that are impartial or imaginative, and that above all are informed by considerations other than the personal interests of the decisionmaker.

Because government officials are engaged by definition in governing, their decisions will often have adverse effects on other persons. When officials are threatened with personal liability for acts taken pursuant to their official duties, they may well be induced to act with an excess of caution or otherwise to skew their decisions in ways that result in less than full fidelity to the objective and independent criteria that ought to guide their conduct.

Courts have extended the legislative immunity doctrine beyond federal and state legislators to other individuals performing legitimate legislative functions. And when a person acts as a legislator, legislative immunity extends to the legislator's aides because their assistance is so critical to the legislator's performance that they must be treated as the latter's alter egos to avoid thwarting the purposes legislative immunity furthers.

In Massachusetts, as in other states, the legislative immunity doctrine is a legal principle that protects individuals acting in a legislative capacity from liability for their legislative actions. This doctrine is rooted in the desire to promote free and open debate within legislative bodies and is designed to serve the public interest rather than individual legislators. It shields not only legislators but also their aides, recognizing the integral role aides play in the legislative process. The doctrine ensures that legislative actors are not deterred from performing their duties by the threat of personal liability, which could lead to overly cautious or biased decision-making. Legislative immunity applies to actions taken in the legitimate performance of legislative functions, and courts have affirmed that it protects such individuals from both liability and the compulsion to testify about their legislative activities. This immunity has been recognized at both the state and federal levels and extends to a range of government officials beyond elected legislators, provided their actions are in the scope of legitimate legislative functions.