Moving to New York City had big influence on Halley’s painting style. Its three-dimensional urban grid led to geometric paintings that engage in a play of relationships between so-called "prisons" and "cells" – icons that reflect the increasing geometricization of social space in the world. Halley began to use colors and materials with specific connotations, such as fluorescent Day-Glo paint, mimicking the eerie glow artificial lighting and reflective clothing and signs, as well as Roll-a-Tex, a texture additive used as surfacing in suburban buildings.

Halley is part of the generation of Neo-Conceptualist artists that first exhibited in New York’s East Village, including Jeff Koons, Haim Steinbach, Mayier Vaisman and Ashley Bickerton. These artists became identified on a wider scale with the labels Neo-Geo and Neo-Conceptualism, an art practice deriving from the conceptual art movement of the 1960s and 1970s. Focussing on the commodification of art and its relation to gender, race, and class, neo-conceptualists question art and art institutions with irony and pastiche.

Halley's works were included in the Sao Paolo Biennale, the Whitney Biennale and the 54th Venice Biennale and represented in such museums and art institutions as the CAPC Musee d'Art Contemporain, Bordeaux; the Museo Nacional Centro de Arte Reina Sofia, Madrid; the Stedelijk Museum, Amsterdam; the Des Moines Art Center; the Dallas Museum of Art; the Museum of Modern Art, New York; the Kitakyushu Municipal Museum of Art; the Museum Folkwang, Essen and the Butler Institute of American Art. Halley lives and works in New York City.