Lanier began his legal career working in Houston for Fulbright & Jaworski in 1984, working in the appellate and trial divisions. In 1990, Lanier founded The Lanier Law Firm. Verdicts have included millions in business fraud, asbestos, and other product-use related lawsuits. Some of Lanier's trials have been carried on the Court-TV website and have been the subject of various articles and books. In 2004 Lanier founded the Christian Trial Lawyers Association. In 2017, Lanier was elected president of the National Trial Lawyers in 2018.
In 2005, Lanier represented Carol Ernst in a lawsuit against Merck & Co., a pharmaceutical company and manufacturer of Vioxx, an anti-inflammatory drug used to treat osteoarthritis and acute pain conditions. Ernst was married to Robert Ernst, a former marathon runner who died after taking the medication. The case was initially decided in Ernst's favor, with a jury awarding her a $253 million verdict. In another case Lanier obtained consumer fraud findings against Merck was it was claimed had misled doctors and patients by concealing information about Vioxx and its risks. The first ruling was overturned on appeal in 2008 with the court noting Lanier "had not proved that Vioxx caused Mr. Ernst’s death" and compensatory damages were reduced in the second.
Lanier has represented plaintiffs in several lawsuits against Johnson & Johnson and DePuy Synthes, which Johnson & Johnson acquired in 1998. The lawsuits allege that DePuy marketed a faulty hip replacement system, despite knowledge that the devices were defective, and that the company failed to warn doctors and patients about the risks involved. This has led to several replacements being removed after failing prematurely. In March 2016, five North Texas residents being represented by Lanier were awarded $497.6 million for alleged complications arising from the hip implants. In November, 2016, Lanier won a lawsuit in which Johnson & Johnson and DePuy were ordered to pay more than $1 billion to six plaintiffs affected by the implants. In 2017, Johnson & Johnson was ordered to pay $247 million to six New York residents Lanier represented who had received the same hip replacements.
In 2018, Lanier led the trial team representing 22 women who had filed suit against Johnson & Johnson. The lawsuit alleged that the company's talcum powder products contained asbestos and that, after several years of use, had caused each of the women's ovarian cancer. The trial lasted six weeks and resulted in $550 million in compensatory damages and $4.14 billion in punitive damages being awarded to the plaintiffs.
Personal life
Lanier is married to Becky and they have five children. He is the brother-in-law of former state representative and former congressional candidate, Kevin Roberts. Lanier funded an opposing super PAC which ran ads against Dan Crenshaw's candidacy for the nomination leading up to the Republican run-off election between Roberts and Crenshaw in the 2018 race to replace retiring Congressman Ted Poe. Lanier appears as himself in the 2011 film Puncture. Lanier has organized several events on behalf of Guatemala SANA, an organization which provides health and education services in Santa Maria de Jesus, a town near Antigua Guatemala.
