In law, a complainant is the person or entity who formally brings a grievance to a court, a law enforcement agency, or an administrative body. The label shows up in civil lawsuits, criminal cases, and workplace discrimination proceedings, but what the complainant actually controls changes a great deal from one setting to the next. In a civil case, the complainant drives the litigation. In a criminal case, the complainant reports what happened and then largely steps aside.
Complainant, Plaintiff, and Petitioner
Many legal references treat “complainant” and “plaintiff” as interchangeable, and in everyday use they often are. A complainant is broadly anyone who files a formal complaint alleging wrongdoing. In a civil lawsuit, that same person is typically called the plaintiff once the case is docketed. If the proceeding starts with a petition instead of a complaint, the filing party is called the petitioner, and the other side is the respondent rather than the defendant. Divorce filings, requests for restraining orders, and appeals usually follow this petition format.
Administrative agencies tend to stick with “complainant.” The Equal Employment Opportunity Commission, for example, uses that label for the person filing a discrimination charge throughout its investigation, even though the same person would be called the plaintiff if the dispute later moved into federal court.1National Archives. EEO Terminology The vocabulary can feel arbitrary, but each label signals which procedural rules govern the case and what kind of relief is available.
The Complainant in a Civil Case
A civil case begins when a complainant files a complaint with the court.2Cornell Law Institute. Federal Rules of Civil Procedure Rule 3 – Commencing an Action That document has to contain a short, plain statement showing why the complainant is entitled to relief. The complainant controls the litigation from there. They choose which claims to bring, decide whether to settle, and carry the responsibility for pushing the case through discovery and trial.
After the complaint is filed, the complainant has to arrange for the defendant to be formally served with a copy of the summons and complaint. The person making that delivery must be at least 18 years old and cannot be the complainant. The complainant can also ask the defendant to voluntarily waive formal service, which saves time and money.3Legal Information Institute. Federal Rules of Civil Procedure Rule 4 – Summons Failing to serve properly is one of the fastest ways to have a case thrown out before it starts.
The Complainant in a Criminal Case
Criminal cases work differently, and this is where the biggest misconception lives. The complainant in a criminal case is the person who reports the alleged crime, but that person does not control whether charges are filed, continued, or dropped. A criminal complaint is a written statement of the essential facts of the offense, made under oath before a magistrate judge.4Office of the Law Revision Counsel. Federal Rules of Criminal Procedure Rule 3 – The Complaint In most jurisdictions, the government files that complaint, not the individual.
Usually the sequence looks like this. Police respond to an incident, gather evidence, and send their findings to the prosecutor’s office. The prosecutor then decides whether to charge the defendant based on the strength of the evidence. Once charges are filed, the case belongs to the state. Even if the complainant no longer wants to proceed, the prosecutor has the authority to continue without their cooperation.5Legal Information Institute. Criminal Complaint The complainant may testify as a witness, but they are not a party to the case the way a civil plaintiff is.
The terminology itself carries weight in a courtroom. Defense attorneys sometimes argue that calling the complainant a “victim” during trial presupposes what the jury is supposed to decide and threatens the defendant’s presumption of innocence. Some courts require the more neutral term “complainant” or “complaining witness” for that reason.
The Complainant in an Administrative Proceeding
Administrative agencies are where the term appears most consistently. The EEOC uses it to identify anyone who files a charge alleging workplace discrimination based on race, sex, religion, national origin, age, or disability.1National Archives. EEO Terminology State consumer protection agencies, professional licensing boards, and housing authorities use the same label.
These proceedings move slower than most people expect. An EEOC investigation can take months or even years, and the complainant keeps that title throughout. Filing deadlines are tight. You generally need to file a charge within 180 calendar days of the discriminatory act, or 300 days if a state or local agency also enforces a similar law.6U.S. Equal Employment Opportunity Commission. Time Limits For Filing A Charge Missing that window can permanently bar the claim, no matter how strong the evidence.
Who Can Be a Complainant
Not everyone who feels wronged can file a complaint that a court will actually hear. Federal courts require a complainant to demonstrate “standing,” which the Supreme Court defined as a three-part test in Lujan v. Defenders of Wildlife:
- Injury in fact. The complainant suffered a concrete, actual harm to a legally protected interest, not a hypothetical or speculative one.
- Causation. The injury is fairly traceable to the defendant’s conduct, not to the independent actions of some unrelated third party.
- Redressability. A favorable court decision would likely fix or compensate for the injury rather than leave it unresolved regardless of the outcome.
All three elements have to be present.7Legal Information Institute. Standing Someone who is genuinely angry about a company’s practices but hasn’t been personally harmed by them lacks standing. The requirement filters out cases brought by people with a political grievance but no personal stake, and it trips up self-represented filers more often than you might expect.
What a Complainant Has to Prove
In most civil cases, the complainant carries the burden of proof. That means they have to convince the judge or jury that their version of events is more likely true than not. This standard is called “preponderance of the evidence,” and it is a lower bar than the “beyond a reasonable doubt” standard used in criminal cases.8Legal Information Institute. Burden of Proof Think of it as tipping the scales slightly in your favor rather than eliminating all doubt.
Administrative proceedings sometimes use different standards. Appeals of agency decisions may apply a “substantial evidence” test, and certain emergency proceedings involving child welfare use an even lower threshold called “some credible evidence.”8Legal Information Institute. Burden of Proof The standard that applies depends on the type of case and the forum, so a complainant should confirm which one governs before building a strategy around the wrong level of proof.
Protection Against Retaliation
Federal law specifically prohibits employers from punishing someone for filing a complaint. Under Title VII, it is unlawful for an employer to discriminate against any employee because that person filed a charge, testified, assisted, or participated in an investigation or hearing.9Office of the Law Revision Counsel. 42 USC 2000e-3 – Other Unlawful Employment Practices The protection covers not just the complainant but also coworkers who cooperate with the investigation.
Retaliation includes anything that might deter a reasonable person from filing a complaint: termination, demotion, reassignment, loss of workplace perks, or hostile treatment from management. Subtler actions count too, like unnecessarily including EEO complaint information in personnel files or mentioning prior complaints during reference checks for future employers.10U.S. Equal Employment Opportunity Commission. Retaliation – Making it Personal Retaliation claims now make up a significant share of all EEOC charges, in part because employers who wouldn’t dream of discriminating sometimes react badly when someone accuses them of it.