Hi Sarah, look, the best way to learn what topic you would want to write about in opposition to the death penalty would be to read about the sociological ramifications of the death penalty. One my suggested reading materials on this topic would be Dr. Lisa Wade's paper titled "The Death Penalty, Race, and the Victim". The reason that I am suggesting you read this material is because it focuses on racial discrimination in society as a reason to oppose death penalty. There are times, when a capital punishment case goes to trial, that the jury becomes predisposed to vote for the death penalty in the event of a guilty verdict based upon certain social conditioning or prejudice in relation to race or color of the accused. Other sociology relevant sources for your preliminary research can include Ben Ambridge's article "Sociologists Test Six Arguments for and Against Capital punishment" That title alone sounds like you can additional research on the topic in continuation of Ambridge's work. Finally, Ted Goertzel also wrote about "Capital Punishment and Homicide: Sociological Realities and Economic Illusions". All 3 of these papers are sociology based discussions in relation to the death penalty. I am sure you will find your research topic within one or all 3 of these articles.
You could use that as the starting point of your research. Once you find a definite topic of interest to you within the research material, you can pursue developing that for your actual research paper. Keep in mind that you should start with a broad topic for research. That way, you can slowly narrow down the focus to something that you will have ample reference material for and also, show a particular interest in discussing. If you can provide that foundation for your paper, writing 4 pages will come easy for you. Good luck with your research. I know you can develop a single topic to research once you become more familiar with the connection of sociology with the death penalty.