Digital investigations, whether forensic in nature or not, require scientific rigor and are facilitated through the use of standard processes. Such processes can be complex in nature. A more comprehensive, generally accepted digital investigation process framework is therefore sought to enhance scientific rigor and facilitate education, application, and research. Previously proposed frameworks are predominantly single-tier, higher order process models that focus on the abstract, rather than the more concrete principles of the investigation. We contend that these frameworks, although useful in explaining overarching concepts, fail to support the inclusion of additional layers of detail needed by various framework users. We therefore propose a multi-tier, hierarchical framework to guide digital investigations. Our framework includes objectives-based phases and sub-phases that are applicable to various layers of abstraction, and to which additional layers of detail can easily be added as needed. Our framework also includes principles that are applicable in varied ways to all phases. The data analysis function intended to identify and recover digital evidence is used as an example of how the framework might be further populated and used. The framework is then applied using two different case scenarios. At its highest level, the proposed framework provides a simplified view and conceptual understanding of the overall process. At lower levels, the proposed framework provides the granularity needed to achieve practicality and specificity goals set by practitioners and researchers alike.