A lawyer for more than thirty-five years, John Williams started his legal career as a lobbyist for Aetna Life & Casualty in Hartford in 1967, following several years working in staff positions in the United States Senate. His introduction to litigation came when company lawyers were asked to donate time to pro bono publico activities of the Hartford County Bar. His first criminal client was Preston ("The Real Thing") Holloway, a man sentenced to life in prison in the 1950s for "use of heroin" in the days before the Fourth Amendment prohibition on illegal searches and seizures was applied to the states. Obtaining his release from prison and a job in the Aetna cafeteria, Williams was quickly disillusioned with corporate liberalism when a Senior Vice President fired Holloway upon learning that thirty years earlier he had suffered from a venereal disease. Forced to return to a life on the streets, he was promptly arrested on other charges and returned to prison.

Leaving Aetna for more useful activity, Williams became chief criminal attorney in the Hill Neighborhood Law Office of the New Haven Legal Assistance Association in the summer of 1969. His first major case was as one of the defense attorneys in the murder prosecution of the local and national leadership of the Black Panther Party, the so-called New Haven Nine. After their acquittal in the summer of 1971, Williams joined Catherine Roraback and Michael Avery, two other Black Panther Party lawyers, in forming New Haven's first public interest law firm. That firm continues today under the name John R. Williams and Associates, LLC.

John Williams is best known as a pioneer in the field of police misconduct litigation. Since 1971, he and his firm have filed most of the police misconduct suits litigated in the federal court in Connecticut. He and his associates have argued many of the Section 1983 appeals decided by the United States Court of Appeals for the Second Circuit in the years since then, and his name and the names of his associates appear on many of the important Second Circuit decisions in this field. He writes and lectures extensively in the area.

His notable Section 1983 cases include Porter v. Nussle, 534 U.S. 516 (2002) (Prison Litigation Reform Act); Liscio v. Warren, 901 F.2d 274 (2d Cir. 1990) (medical treatment of prisoners); Cartier v. Lussier, 955 F.2d 841 (2d Cir. 1992) (misrepresentations in arrest warrant applications); Mozzochi v. Borden, 959 F.2d 1174 (2d Cir. 1992) (release-dismissal agreements); Dobosz v. Walsh, 892 F.2d 1135 (2d Cir. 1989) (police whistleblowers); Musso v. Hourigan, 836 F.2d 736 (2d Cir. 1988) (free speech at public meetings); Reed v. Town of Branford, 949 F. Supp. 87 (D. Conn. 1996) (age discrimination as a &1983 violation and harassment as a substantive due process violation); Gavlak v. Town of Somers, 267 F. Sup. 2d 214 (D. Conn. 2003) (rights of property owners in zoning disputes); In re Alexander V., 223 Conn. 557, 613 A.2d 780 (1992) (familial relationships as a fundamental constitutional right); Warren v. Dwyer, 906 F.2d 70 (2d Cir. 1990) (submission of qualified immunity question to jury); Gagnon v. Ball, 696 F.2d 17 (2d Cir. 1982) (police bystander liability); Pitchell v. Callan, 13 F.3d 545 (2d Cir. 1994) (color of law); Miller v. Lovett, 879 F.2d 1066 (2d Cir. 1989) (pendent jurisdiction); Dodd v. City of Norwich, 827 F.2d 1 (2d Cir. 1987) (municipal liability); Pouncey v. Ryan, 396 F. Supp. 126 (D. Conn. 1975) (Newman, J.) (collateral estoppel effect of prior conviction); O'Neill v. Krzeminski, 839 F.2d 9 (2d Cir. 1988) (standard for punitive damages); and Ruggiero v. Krzeminski, 928 F.2d 558 (2d Cir. 1991) (opportunity cost as a factor in attorney fee awards).

He also is an active criminal practitioner. His celebrated cases include the Lorne Acquin mass murder case in Prospect, Connecticut, in 1977 which remains the largest mass murder case ever prosecuted in the State of Connecticut. He represented members of the Black Panther Party in the so-called "New Haven Nine" prosecutions between 1969 and 1971, members of the Black Liberation Army, Los Macheteros, and other controversial cases. He has argued countless appeals in the Connecticut Supreme Court in both criminal law and other areas of the law. He has contributed to the expansion of rights for criminal defendants under the state constitution, going beyond the protections afforded by the federal Bill of Rights. State v. Joyce, 229 Conn. 10, 639 A.2d 1007 (1994).

He takes particular pride in his efforts to reshape and democratize the Connecticut jury system. In 1976, he was the first Connecticut lawyer to challenge in federal court the then common prosecutorial practice of using "peremptory challenges" to remove minorities from juries in criminal cases. United States v. Newman, 549 F.2d 240 (2d Cir. 1977).

Throughout the entire decade of the 1970s and into the 1980s, in a series of state and federal court cases, he fought many court battles to change the method by which Connecticut juries were selected, a complex legacy of the colonial era which produced juries that were disproportionately white, male, middle-aged and suburban. Finally, in 1986, in the companion cases of Alston v. Manson and Haskins v. Manson, 791 F.2d 255 (2d Cir. 1986), he persuaded the United States Court of Appeals to strike down the Connecticut system.

In the cases of State v. Anthony, 172 Conn. 172, 374 A.2d 156 (1976); and State v. Roberson, 173 Conn. 102, 376 A.2d 1087 (1977); he persuaded the Connecticut Supreme Court to prohibit trial court judges from limiting the time lawyers could question prospective jurors during the jury selection process, thereby reducing the danger of biased jurors infecting trials with racial and other prejudices.

One of his most celebrated cases was the New Haven Wiretap Litigation class action in the federal court in Connecticut running from 1977 to 1984, in which he represented more than 1,000 people from all walks of life and strata of society who had been victimized by an unlawful wiretap operation conducted jointly by local police and FBI agents for more than a decade. This litigation resulted in a settlement of over $1 million, led to significant reforms in the area of personal privacy, and generated a voluminous history of illegal police surveillance of the Black Panther Party which is now archived at Yale's Beineke Library.

He has worked extensively, and sometimes successfully, in cases involving the "false confession syndrome," in which innocent people have confessed to crimes they did not commit. E.g., Miller v. Angliker, 848 F.2d 1312 (2d Cir.), cert. denied, 488 U.S. 890 (1988); State v. LaPointe, 237 Conn. 694, 678 A.2d 942 (1996). He was the first lawyer in the United States to win an acquittal in a criminal case on the ground that the ingestion of prozac caused the criminal behavior. State v. DeAngelo, 2000 WL 973104 (Conn. Super. 2000).

In the civil arena, his cases have significantly expanded the rights of plaintiffs in such fields as the intentional infliction of emotional distress and vexatious litigation [DeLaurentis v. City of New Haven, 220 Conn. 225, 597 A.2d 807 (1991)]; the rights of divorced persons to sue their former spouses for marital torts [Delahunty v. Massachusetts Mutual Life Ins. Co., et al., 236 Conn. 582, 674 A.2d 1290 (1996)]; the right of parents to sue public school systems for educational inadequacies [Bell v. Board of Education, 55 Conn. App. 400, 739 A.2d 321 (1999)]; the rights of gays to equal treatment in child-visitation cases [Zavatsky v. Anderson, 130 F. Supp. 2d 349 (D. Conn. 2001)]; and the appellate rights of parties in workers compensation cases [Cantoni v. Xerox Corp., 251 Conn. 153, 740 A.2d 796 (1999)]. Other notable appellate cases include Davis v. Margolis, 215 Conn. 408, 576 A.2d 489 (1990) (qualifications for expert witnesses in legal malpractice cases); DeLeo v. Nusbaum, 263 Conn. 588 (2003), which established the "continuous representation rule" for statute of limitations purposes in legal malpractice cases; and Drumm v. Brown, 245 Conn. 657, 716 A.2d 50 (1998), limiting the "exhaustion of tribal remedies" bar to suits against Indian tribes and their leaders.

In recent years, he has devoted considerable energy to protecting the rights of high school girls, who have been the victims of sexual assault or harassment, to fair treatment by school officials.  He has had a lot of success in pursuing litigation for these young women in the federal courts pursuant to Title IX of the Civil Rights Act.  His victories have included Doe ex rel. A.N. v. East Haven Board of Education, 430 F. Supp. 2d 54 (D. Conn.), affirmed 200 Fed. Appx. 46 (2nd Cir. 2006); Doe ex rel. Doe v. Derby Board of Education, 451 F. Supp. 2d 438 (D. Conn. 2006); and Riccio v. New Haven Board of Education, ___ F. Supp. 2d. ___, 2006 WL 3826687 (D. Conn. 2006).