Lieutenant junior grade Walter J. Pierce was a Starfleet engineer. According to medical file M2-013-7, he was born on stardate 15720.4 on the planet Epsilon Indi II. He was the son of Anita R. and Ambrose W. Pierce. He graduated from Starfleet Academy, San Francisco, Earth on stardate 37293.7.

Pierce had been assigned to the USS Chicago on stardate 37719.4, the USS Umibozu on stardate 38408.8, the USS Suleiman on stardate 38878.2, and the USS Enterprise-D on stardate 39471.9. He was awarded the Huntley Award for subspace research on stardate 38528.4, the Jahal Award for warp field engineering on stardate 37782.4, and the Macalintal Science Ribbon (with cluster) on stardate 37182.7.

In the early 2360s, he was a power systems engineer at the Utopia Planitia Shipyards constructing the Enterprise-D. He served as assistant team leader installing engineering power conduits and the warp engine local control systems.

In 2362, he murdered his girlfriend Marla E. Finn and her lover in a jealous rage and then killed himself by jumping into the plasma stream of the Enterprise-D.

Pierce was part Betazoid – his maternal grandmother was a Betazoid, and this left empathic traces in the nacelle tube bulkhead. These traces affected others with empathic lineages and one crewmember, Daniel Kwan, killed himself in 2370. While investigating his death, Deanna Troi was also affected, but was saved at the last moment by Lieutenant Worf.

Troi perceived numerous details about Pierce's life through his illusory personnel file when she detected his empathic memory traces. (TNG: "Eye of the Beholder")