  Context: An assurance case is a structured hierarchy of claims aiming at
demonstrating that a given mission-critical system supports specific
requirements (e.g., safety, security, privacy). The presence of assurance
weakeners (i.e., assurance deficits, logical fallacies) in assurance cases
reflects insufficient evidence, knowledge, or gaps in reasoning. These
weakeners can undermine confidence in assurance arguments, potentially
hindering the verification of mission-critical system capabilities.
  Objectives: As a stepping stone for future research on assurance weakeners,
we aim to initiate the first comprehensive systematic mapping study on this
subject. Methods: We followed the well-established PRISMA 2020 and SEGRESS
guidelines to conduct our systematic mapping study. We searched for primary
studies in five digital libraries and focused on the 2012-2023 publication year
range. Our selection criteria focused on studies addressing assurance weakeners
at the modeling level, resulting in the inclusion of 39 primary studies in our
systematic review.
  Results: Our systematic mapping study reports a taxonomy (map) that provides
a uniform categorization of assurance weakeners and approaches proposed to
manage them at the modeling level.
  Conclusion: Our study findings suggest that the SACM (Structured Assurance
Case Metamodel) -- a standard specified by the OMG (Object Management Group) --
may be the best specification to capture structured arguments and reason about
their potential assurance weakeners.
