MaryAnn Joerres



  • Marquette University Law School (1985)
  • Marquette University (1981)

Areas of Practice:

Admitted to Practice:

  • Texas
  • U.S. Court of Appeals, 5th Circuit
  • U.S. District Courts for the Northern and Western Districts of Oklahoma
  • U.S. District Courts for the Northern, Southern, Eastern and Western Districts of Texas
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MaryAnn Joerres


(214) 389-5309

[email protected]

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MaryAnn Joerres is a Dallas-based Diamond McCarthy partner. She works on a variety of civil litigation matters, including lender liability and disputes involving financial institutions, securities fraud, antitrust, engineering malpractice, toxic torts, products liability, oil and gas, and ERISA.

MaryAnn has been involved in a number of high-profile cases since joining Diamond McCarthy in 2001. She defended a large gas producing company in a number of proposed class action cases involving the propriety of royalty payments for gas and natural gas liquids production in Texas. She also defended an international financial company, a national mortgage company and others in a case alleging improper declaration of default under the loan agreements and refusal to deal with the plaintiffs in good faith.

Before joining Diamond McCarthy, MaryAnn was a partner at a prominent Dallas law firm. She began her legal career in the Chicago office of a major national firm where she worked in antitrust and securities litigation.

MaryAnn has spoken on a variety of legal topics, including class actions and disputes involving mineral interests and royalty payments, to the Southwestern Legal Foundation, the Energy Section of the Dallas Bar Association, the American Association of Professional Landmen and the Dallas Association of Petroleum Landmen.

Licensed to practice law in Texas, MaryAnn is also admitted to practice before the U.S. District Courts for the Northern, Southern, Eastern and Western Districts of Texas; the U.S. District Courts for the Northern and Western Districts of Oklahoma; and the U.S. Court of Appeals for the 5th Circuit.

  • Defense of a large gas producing company in a number of proposed class action cases involving the propriety of royalty payments for gas and natural gas liquids production in Texas. The Plaintiffs' claims focused on affiliate sales and the pricing structure of such sales. Classes were certified at the trial court level, but defendants were successful in reversing them on appeal. See See, e.g., Union Pacific Resources Group v. Hankins, 111 S.W.3d 69 (Tex 2003); Union Pacific Resources v. Neinast, 67 S.W.3d 275 (Tex. App.- Houston [1st Dist.] 2001, pet. denied);
  • Defense of a large oil producing company in an action brought under the False Claims Act, 31 U.S.C. § 3729, et seq. in the United States District Court for the Eastern District of Texas. The case was originally filed by private relators on behalf of the United States under the qui tam provisions of the False Claims Act. The Plaintiffs alleged that the defendant oil companies had engaged in numerous schemes, and had filed hundreds of thousands of false reports with the Department of Interior, with the intent to underpay royalties on crude oil extracted from federal and Indian lands.
  • Defense of the second largest gas producer in the state of Michigan in a proposed class action involving the propriety of royalty payments for gas and natural gas liquids production. Plaintiffs' claims focus on affiliate sales, the pricing of such sales, and the deductions taken therefrom in the calculation of royalty payments. After first reversing a default judgment taken prior against the company prior to involvement of attorneys, the first also reversed the trial court's certification of a royalty owner class. Upon securing the reversal, plaintiffs' counsel agreed to dismiss the case with prejudice.
  • Defense of a large independent natural gas producer in cases brought by landowners in/near Fort Worth, Texas. Plaintiffs alleged that the industry players in the area (including our client) conspired against landowners/prospective royalty owners to drive down the price of bonus payments and royalties. Defendants (producers, brokers and related industry players) moved to dismiss the case based standing/lack of subject matter jurisdiction grounds. The judge recently granted defendants motion and dismissed the antitrust claims.
  • Representation of an exploration company showing that they suffered the brunt in trades of undeveloped reserves and other land and mineral trades with former partners, prospective partners and other mineral interest owners, as well as defending against ownership/title contests as to certain mineral interests.  
  • Represented and provided oil and gas expertise for an officer of an energy company.  The focus in the adversary litigation that came out of the bankruptcy was primarily related to the valuation of reserves and the accuracy of the reporting of the reserves, as well as whether our client was part of a misrepresentation of the company's reserves to its lenders, owners and others.  
  • Prosecution of a third party claim seeking recognition of the validity of obligations under a natural gas gathering contracts in Texas. Issues involved the validity of assignments, which parties were obligated under the contracts, and the fees to be charged thereunder. The case was settled with recognition of the contract rights and agreed fee caps.
  • Representation of a natural gas producer in connection with the terms of a gas sales agreement. The issues included the construction of contractual language, whether terms were enforceable and whether there was to be an equity kicker/upside, and the effect of the juries answer to several questions. The case (which was litigated in Texas although the production was in Michigan) was ultimately settled after the producer rescinded the contract based upon the jury findings and cross appeals were filed.
  • Defense of a large oil producing company in a number of related proposed class action cases involving the propriety of royalty payments for crude oil production and the use of posted prices in connection therewith. Plaintiffs brought the cases on behalf of classes of royalty owners (varying in geographic scope). For purposes of effectuating a global (nation-wide) settlement, defendants agreed to consolidate this group of cases into a Multi-District Litigation proceeding in federal court with another series of similar cases. After evidentiary hearings, and over objections by certain proposed class members, the District Court certified the settlement class and approved the settlement. The objectors appealed the settlement. Those appeals have been unsuccessfully exhausted, and payouts pursuant to the settlement have been completed.
  • Defense of environmental claims against a company that had recently purchased several gas processing plants. A neighboring landowner of one of the plants filed trespass, nuisance, and personal injury claims relating to operations both before and after the acquisition.
  • Two month trial on behalf of a minority shareholder against the majority shareholder and nominally against the closely held corporation for minority shareholder oppression, breach of contract, derivative claims against the majority shareholder for misuse of corporate assets and several other related claims. The minority shareholder was successful on all claims presented to the jury. The jury found oppression and that the majority shareholder had acted against the interests of the company. Final judgment was recently entered -- requiring the company to pay an $85 million dividend, back-pay to the minority shareholder, reimbursement to the corporation as well as attorneys fees on the contract claims and the derivative claims brought against the majority shareholder.
  • Defense of an international civil/environmental engineering firm against a multi-million dollar claim for professional malpractice regarding the design, and management of construction, of a large wastewater treatment plant.
  • Defense of a manufacturer of cadmium and nickel batteries in a toxic tort case. Motions for summary judgment resulted in a leading published opinion regarding the use of experts, particularly in toxic tort cases. Christopherson v. Allied Signal, 939 F.2d 1106 (5th Cir. 1992).
  • Defense of an international financial company, a national mortgage company and other defendants in a case brought on behalf of a hotel developer and various companies in which he and his partners had an interest. Plaintiffs alleged that defendants improperly declared a default under the loan agreements and refused to deal with plaintiffs in good faith. Plaintiffs' claims included breach of contract, fraud, and tortious interference with contract. The case was ultimately settled with plaintiffs dismissing all of their claims and the defendants obtaining a confidential and sealed agreed judgment on defendants' counterclaims.
  • Defense of a major bank holding company in a series of multi-million dollar lawsuits involving the correspondent lending relationship between the client's subsidiary banks and other non-affiliated banks and the non-affiliated bank's issuance of commercial paper. The claims included RICO, alleged securities law violations and antitrust violations and other lender liability theories.
  • A two and a half month trial, representing one of the country's leading life insurance companies and lenders to the hotel industry in a multi-million dollar case brought against it by one of its borrowers on claims of lender liability, alleged antitrust violations and unfair competition. Jury verdict rendered in favor of client - requested award entered on client's counterclaims and a take-nothing judgment on the borrower's claims.
  • Prosecution of a class action suit on behalf of a class of employees (and their beneficiaries) of a large corporation in the defense industry, claiming breaches of ERISA, fiduciary duties and other applicable laws in connection with their multi-part pension plan. A class and subclass was certified. The case was settled and the settlement approved by the Court at the final fairness hearing.