Derek P. Sieck Personal Injury & Workers’ Comp Attorney
Derek Sieck combines a finance background with legal expertise to maximize compensation for injured clients across Missouri, Illinois, and Kansas. With over $7 million in documented settlements—including a $2.65 million medical malpractice recovery—Derek has built a track record of results in complex personal injury cases. He is particularly known for representing union workers in construction accident and workers’ compensation cases, fighting to protect the men and women who build our communities.
⚖️ $7+ Million in Documented Settlements
⚖️️ Union Worker Advocate – Construction & Workers’ Comp Cases
⚖️ Licensed in 3 States – Missouri, Illinois & Kansas
“I represent union workers throughout the area—the men and women who build our communities deserve an attorney who will fight just as hard for them when they’re injured on the job.”
Derek P. Sieck
Personal Injury Attorney
Proven Results
In just eight years of practice, Derek has secured millions for injured clients across multiple practice areas—from medical malpractice to construction accidents to auto collisions. His finance background helps him accurately calculate and present damages to maximize client recovery.
$7M+
In Settlements
Documented case results for injured clients
$2.65M
Largest Settlement
Medical malpractice case
3
State Licenses
Missouri, Illinois & Kansas
8
Years of Experience
Personal injury litigation
Representative Case Results
Derek has secured significant settlements across medical malpractice, premises liability, auto accidents, and products liability. Below are representative results demonstrating his ability to maximize compensation for injured clients. Past results do not guarantee future outcomes. Each case is unique.
$2.65 Million — Medical Malpractice
Confidential settlement in a medical malpractice case. When healthcare providers fail to meet the standard of care, the consequences can be devastating. Derek fights to hold negligent medical professionals accountable and secure full compensation for victims of medical errors.
$2.275 Million — Products Liability
Settlement for a client injured by a defective product. Derek has trial experience in products liability cases and understands how to build compelling cases against manufacturers who put profits before consumer safety.
$1.25 Million — Car Accident
Settlement for a client injured in an automobile accident. Derek’s finance background helps him accurately calculate both current and future damages to ensure clients receive compensation that reflects the true cost of their injuries.
$1 Million (x2) — Premises Liability
Two separate $1 million settlements in premises liability cases. Property owners must maintain safe conditions—when they fail and someone is injured, Derek holds them accountable for the full extent of the harm caused.
We Don’t Just Take On Cases—We Take On Causes.
Whether you’ve been injured on a construction site, in a car accident, or through medical negligence, Derek Sieck doesn’t just fight for compensation—he fights to ensure what happened to you never happens to another family. His track record of million-dollar results demonstrates his commitment to maximizing recovery for every client.
Peer Recognition & Credentials
Bar Admissions
Missouri – 2014
Illinois – 2015
Kansas – 2015
U.S. District Court, Eastern District of Missouri
Professional Associations
Missouri Association of Trial Attorneys (MATA)
Bar Association of Metropolitan St. Louis (BAMSL)
Trial Experience
Derek has taken cases to trial in both products liability and workers’ compensation matters. This trial experience gives him credibility in settlement negotiations—insurance companies know he’s willing to go to court when necessary to fight for his clients.
Derek’s Practice Areas
Derek handles a wide range of personal injury cases across Missouri, Illinois, and Kansas, with particular experience representing union workers in construction accidents and workers’ compensation claims. His finance background helps him accurately calculate damages to maximize client recovery.
Motor Vehicle Accidents
Car crashes, truck accidents, motorcycle collisions—Derek handles all types of motor vehicle accident cases. His $1.25 million car accident settlement shows his commitment to maximizing compensation for accident victims.
Property owners must maintain safe conditions for visitors. When they fail, Derek holds them accountable—as demonstrated by his two separate $1 million premises liability settlements.
Traumatic brain injuries, spinal cord damage, and other life-altering injuries require attorneys who understand both the immediate and long-term impacts. Breanna works closely with medical professionals to ensure her clients receive proper care while fighting for full compensation.
Derek’s $2.65 million medical malpractice settlement demonstrates his ability to take on complex medical negligence cases. When doctors, hospitals, or healthcare providers fail to meet the standard of care, he holds them accountable.
Defective products injure thousands of consumers every year. Derek has trial experience in products liability cases and has secured a $2.275 million settlement for a client harmed by a dangerous product.
Injured workers deserve an attorney who understands the workers’ compensation system and will fight for maximum benefits. Derek has trial experience in workers’ comp cases and represents union workers across Missouri, Illinois, and Kansas.
The law always interested Derek from a young age. After talking with family members who were lawyers, he decided to pursue a legal career—combining his natural interest in law with a solid foundation in finance.
University of Iowa
B.A. Finance – 2014
Derek earned his undergraduate degree in Finance from the University of Iowa. This background helps him accurately calculate and present economic damages in personal injury cases—ensuring clients receive compensation that reflects the true financial impact of their injuries.
Saint Louis University School of Law
Juris Doctor – 2017
Derek earned his law degree from SLU Law, one of the region’s leading law schools. He was admitted to the Missouri Bar in 2014, followed by Illinois and Kansas in 2015.
OnderLaw
Personal Injury Attorney
At OnderLaw, Derek focuses on single-event personal injury cases, with particular emphasis on representing union workers in construction accidents and workers’ compensation matters. He also handles automobile accidents and medical malpractice cases, having secured over $7 million in documented settlements.
OnderLaw Awards & Recognition
Recognized as Top 1-2% of Attorneys Nationwide
When Your Case Becomes Our Cause
Derek Sieck and the OnderLaw team don’t just fight for compensation—we fight to ensure what happened to you never happens to another family. If you’ve been injured on the job, in an accident, or through medical negligence, let’s discuss how your case could create lasting change.
