A Supreme Court ruling could affect thousands of compensation claims by people whose relatives died after developing an asbestos-related cancer, lawyers say.
Mesothelioma victims' families asked the UK's highest court to clarify the law relating to insurance claims at a hearing in London in December.
Five Supreme Court justices, who were asked to consider whether liability was "triggered" at the time of exposure to asbestos or at the onset of symptoms, will deliver judgment in London.
Relatives of workers who died from mesothelioma - after inhaling asbestos fibres during their employment - want to make claims on insurance policies covering periods from the late 1940s to the late 1990s.
Judges, headed by Supreme Court president Lord Phillips, heard appeals arising out of six separate test cases.
Specialist solicitor Helen Ashton, who works for law firm Irwin Mitchell, who is representing one of the lead claimants, said she hoped the Supreme Court could "provide clarity".
"The litigation concerns the appropriate trigger for employers' liability insurance policies in relation to asbestos-related mesothelioma claims where the wording of the policy requires injury or disease to an employee to be 'sustained' or 'contracted' during the period of insurance," she said. "The case is set to impact on thousands of mesothelioma claims in the future which, given the predicted number of cases to emerge, is estimated to be worth over £100 million to the insurers involved in the litigation."
Insurers won a partial victory in 2010 when the Court of Appeal found only some sufferers could recover damages for the injuries they sustained at work decades ago.
Three appeal judges were unable to agree on a High Court ruling - given in November 2008 and hailed as a victory for victims - that employers' insurers at the time of exposure were liable to pay out on claims. Instead, they found that in some cases the responsibility lay with the employers' insurers at the onset of symptoms, which in some cases was 50 to 60 years later.
The appeals before the Supreme Court arose from the deaths from mesothelioma of employees who inhaled asbestos fibres during employment. Lawyers said the appeal court ruling left many claimants facing more "confusion and uncertainty".