Kate Spencer (died May 2014) was the district attorney of Starling City. She was to be the prosecutor had Oliver Queen's case gone to trial, and headed Moira Queen's on her role in the Undertaking. During the Siege, Kate was killed by one of Slade Wilson's soldiers.
Kate apparently failed to prosecute Martin Somers, likely due to his connections in the district attorney's office. However, after The Hood obtained a recording of Somers confessing to ordering Victor Nocenti's murder, Kate had enough evidence to send Somers to prison for the rest of his life.
When Oliver Queen was arrested on suspicion for being The Hood, Kate was brought on as the prosecution and was visibly taken aback at Oliver's desire to represent himself. When the hearing commenced, Kate refused to consider bail and deemed Oliver a "flight risk", citing the Queen family's extensive wealth. Laurel Lance intervened and suggested a minimized risk by keeping Oliver on house arrest. Judge Moss agreed, overriding Kate's objections.
Kate admitted that she believed Oliver to be the vigilante, though due to being affected by post-traumatic stress disorder from being stranded on an island for five years, and offered him the insanity plea. Oliver rejected the deal in favor of a polygraph, with the agreement that if he were to fail, he would accept the plea. The case was thrown out when Oliver was (seemingly) proved innocent.
After career criminal Cyrus Vanch was released from Iron Heights, Kate informed Anastasia at CNRI that she couldn't take legal action against him without sufficient evidence and requested that Cyrus' prosecutors not stop by her office to demand help.
Kate apologized to Laurel for Adam's actions with saying that he had no authorization to give her her job back and said that nothing changed, but revealed that he was no longer employed for trying to capture Helena Bertinelli. However, Laurel threatened to expose Adam's involvement if Kate didn't rehire her. Kate complied and stated that she was surprised, thinking blackmail was beneath Laurel.
After Quentin Lance was attacked in prison, Kate went to visit him and Laurel threatened to sue her if she didn't drop the charges against Quentin for working with the vigilante. Kate agreed to authorize this. However, as Laurel left, Kate warned her to pick her battles, as they wouldn't always go her way.
- In the DC comics multiverse, Kate Spencer is also known as the vigilante Manhunter.