An intruder barrier is provided that includes multiple generally parallel transparent slats acting as burglar bars with at least some, and preferably all, of the transparent slats having associated therewith a conductive path extending at least from a first end region of a slat to a second end region thereof. The conductive path is capable of conducting electricity or electromagnetic radiation along the length of the slat and is associated with an output to an alarm system that may be configured to trigger an alarm when the conductive characteristic of a slat is terminated by virtue of the slat being at least partially severed, broken, or removed from its operative position. Typically the transparent slats are secured to a fixed surrounding frame of an opening window. The invention in a further embodiment includes transparent slats for use in such an intruder barrier. The invention in a further embodiment includes a laterally collapsible latticed intruder barrier comprising multiple transparent slats interconnected with each other and having such conductive paths.