Each specialty field has its own requirements for possible testing, its own protocols, and its own procedures. A key part of your contribution is to know your field well enough to design each test and then run or witness them. If professionals in your field by and large rely on third parties to run tests, such as independent laboratories, specify that fact and tell the labs explicitly which tests to run, and how to run them. The legal burden is that the tests are run under conditions substantially the same as existed at the time of the event in question.
If your tests are part of standard protocols or methodologies in your discipline, follow procedures similar to those described in peer-reviewed publications. In other word run tests according to commonly accepted guidelines. If your tests require multiple passes to secure a series of results or data values, run them enough times to justify the results quantitatively.
Your expert opinions will rely on the results you secure from tests. The results of your tests are only as valid as the tests. Remember, you may be asked why you ran specific tests, why you used or specified individual parameters, and why other tests were not run. You should be able to describe the logic and methodology that led you to the particular tests, and why the results led to your opinions. If your tests show inconsistencies, you must be able to explain them. If some tests in your industry have known error fees, secure documentation in advance about them and make sure to correlate observed error fees during your tests with the known industry rates.
If the case focuses on equipment that failed, run tests to explain the cause of the failure, and define your tests to show whether the problems lay in original design, follow-on manufacturing, or even usage by company personnel or consumers. And make sure any equipment used to test other equipment or evidence has undergone regular maintenance and / or calibration if required.  secure detailed documentation of the service and keep this information in your own file folder as well. If an opposing attorney determines that you or your laboratory did not maintain or properly calibrate testing equipment, then the judge may dismiss the results. If the equipment does not require calibration, perhaps because results are relative and not absolute, you should know that so that you can testify to it.
In the computer field, software and operating systems change regularly. In the construction field, building codes change frequently. In aviation, both planes and avionics change from time to time. Maintaining records of these developments will be useful; some legal matters you face will involve the state of your discipline years earlier. Legal cases sometimes involve equipment that has been operating for many years at company facilities.
Having your own reference materials will permit you to rapidly find data to help with your analyses. This could range from printed copies of articles to copies of journals and magazines to computer files.
At the same time, you should know about the latest published developments in your field. Failing to use the current tools of your trade, or software in your specialty, or technology in your science, may be enough to exclude your opinions from court. To be the best expert witness possible, you must keep your experience current.
Many specialty fields have their own journals or magazines; stay familiar with published developments in your field to ensure that you can select and use the most recent techniques for research and analysis. Using search engines on the web is convenient to Discover the latest research. Current information often appears on websites for companies doing the research before it appears in professional journals.

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