What Proof Do You Need for a California Roundup Lawsuit?

Thousands of people across the country have filed lawsuits alleging that their exposure to Roundup, the world’s most popular weedkiller, caused them to develop non-Hodgkin lymphoma and other serious cancers. These lawsuits argue that Monsanto (and its parent company, Bayer) knew about the cancer risks associated with glyphosate, Roundup’s active ingredient, but failed to warn the public.

If you or a loved one used Roundup and later received a cancer diagnosis, you may be considering legal action. However, filing a successful lawsuit requires more than just a suspicion of a link. A strong case is built on solid, convincing evidence. Understanding what proof you need is the first and most critical step in the legal process.

At Walch Law, we are here to help. One call with us will help you determine if you have a case and how much it might be worth. Call the winning Roundup team at Walch Law now to learn more.

The Two Pillars of a Roundup Lawsuit: Exposure and Causation

Every successful Roundup lawsuit rests on two fundamental pillars:

Proof of Exposure: You must demonstrate that you were significantly exposed to Roundup over a period of time.
Proof of Causation: You must show that your exposure to Roundup was a substantial factor in causing your specific medical diagnosis, most commonly non-Hodgkin lymphoma.

Building these two pillars requires gathering specific types of documentation and testimony. Let’s look at each one in detail.

1. Proving Your Exposure to Roundup

To start, you must prove that you actually used Roundup or were exposed to it in another way. A one-time use from decades ago is unlikely to be sufficient. The goal is to create a detailed history that shows consistent and significant contact with the product.

Key Evidence for Proving Exposure:

Purchase Records: This is some of the strongest evidence you can provide. Dig through old records to find receipts, credit card statements, or invoices from stores like Home Depot, Lowe’s, Walmart, or local garden centers that show purchases of Roundup products. Even if the records are old, they can be invaluable.
Employment Records: Many plaintiffs were exposed to Roundup at work. Landscapers, groundskeepers, farmworkers, and agricultural employees often have the most significant exposure. Employment records, pay stubs, job descriptions, or testimony from former colleagues or supervisors can help establish that using glyphosate-based herbicides was a regular part of your job.
Photographs and Videos: Do you have any photos or videos of yourself, your property, or your workplace that show Roundup containers in the background? A picture of you spraying your yard or a shot of the shed with Roundup bottles on the shelf can serve as powerful visual proof.
Witness Testimony: Testimony from family members, neighbors, or coworkers who saw you using Roundup regularly can be very persuasive. They can attest to the frequency and duration of your use, helping to paint a clear picture of your exposure history.
Your Own Testimony and Records: Your personal account is crucial. An attorney will help you create a detailed timeline of your Roundup use. You should document:
- When you started using Roundup.
- How many years you used it.
- How often you used it (e.g., weekly during the summer, monthly year-round).
- The specific Roundup products you used.
- How you applied it (e.g., handheld sprayer, backpack sprayer).
- Whether you wore protective gear like gloves or a mask.

It is important to be as detailed and accurate as possible. The more comprehensive your exposure history, the stronger this part of your case will be.

2. Proving Your Medical Diagnosis and Causation

Once exposure is established, you must connect it to your medical condition. This involves providing detailed medical documentation and leveraging scientific evidence to show that Roundup was a likely cause of your illness.

Key Evidence for Proving Medical Causation:

Complete Medical Records: This is the cornerstone of your medical proof. Your attorney will need to gather all medical records related to your diagnosis and treatment. This includes:
- Biopsy results and pathology reports that confirm your diagnosis of non-Hodgkin lymphoma or another related cancer.
- Notes from your primary care physician and oncologists.
- Records of all treatments, including chemotherapy, radiation, and surgery.
- Results from blood tests, CT scans, PET scans, and other diagnostic imaging.
Medical Expert Testimony: This is arguably the most critical component of proving causation. An attorney will retain qualified medical experts, such as oncologists and toxicologists, to review your case. These experts will provide a professional opinion on whether your exposure to glyphosate was a substantial contributing factor to your cancer. Their testimony will bridge the gap between your exposure history and your medical diagnosis, drawing on established scientific research that links glyphosate to cancer.
Scientific Studies: While you will not be gathering these yourself, your legal team will use a large body of scientific research as a foundation for your case. Studies from organizations like the International Agency for Research on Cancer (IARC), which classified glyphosate as “probably carcinogenic to humans,” are central to all Roundup lawsuits. These studies provide the scientific backing for your expert’s opinion.

Ruling Out Other Causes

As part of the legal process, the defense will try to argue that other factors caused your cancer. They may point to family history, smoking, or other potential risk factors. Your legal team must be prepared to address these arguments. Your medical records and expert testimony will be used to demonstrate that, even considering other potential factors, your Roundup exposure played a substantial role in the development of your illness.

How an Experienced Roundup Law Firm at Walch Law Can Help

Gathering all of this evidence and weaving it into a compelling legal argument is a monumental task. It is not something you should ever attempt to do alone. An experienced Roundup lawsuit attorney is essential for several reasons:

Knowing What to Look For: A skilled attorney knows exactly what types of evidence are needed and where to find them. They can help you recall details of your exposure history you might have forgotten and identify key documents.
Access to Experts: Top law firms have established relationships with leading medical and scientific experts whose testimony is credible and persuasive in court.
Handling the Legal Legwork: Your attorney will handle the complex process of subpoenaing records, filing motions, and navigating the court system. This allows you to focus on your health and your family.
Building the Strongest Case: They will compile all the evidence—your exposure history, medical records, and expert opinions—into a powerful narrative that clearly demonstrates to a judge and jury how Roundup caused your suffering.
Fighting the Opposition: Bayer’s legal team is formidable. You need an advocate on your side who is not afraid to stand up to a massive corporation and fight for your rights.

If you believe your cancer was caused by Roundup, the most important step you can take is to speak with an attorney at Walch Law NOW. They can evaluate your situation, help you understand the proof required, and guide you on the path toward securing the justice and compensation you and your family deserve.