1. A system for facilitating information analysis tasks comprising: a data processing system configured to execute a visualisation tool comprising: an information retrieval system for browsing and extracting a plurality of information excerpts from information sources for display of the extracted information excerpts; in the user interface via received user input to define the information excerpts; a user interface for marshalling evidence, said user interface configured to provide a space within which to visually display information excerpts represented as information objects for visual cognition, wherein the user interface is configured to represent the information objects as objects movable in said space; an assertion group object displayed on the user interface to refute or support an assertion, the assertion group object having at least one assertion gate for supporting the assertion and at least one assertion gate for refuting the assertion, the assertion group object monitors the position of the movable information objects relative to the location of the assertion gates and determines the connection of the information objects to the assertion automatically; wherein the assertion gates are visually represented on the user interface and the assertion gates provide visual indication when an information object is moved through them.