“There is one and only one social responsibility of businesses,” Wrote Milton Friedman, a Nobel prize-winning economist, “That is,to use its resources and engage in activities designed to increase its profit”. But even if you accept Firedman’s premise and regard corporate social responsibility (CSR) policies as waste of shareholders’ money, things may not be absolutely clear-cut. New research suggest the CSR may create monetary value for companies-at least when they are prosecuted for corruption.
The largest firms in America and Britain together spend more than $15 billion a year on CSR,according to an estimate by EPG, a consulting firm.This could add value to their businesses in three ways. First, consumers may take CSR spending as a “signal” that a company’s products are of high quality. Second, customers may be willing to buy a company’s products as an indirect way to donate to the good causes it helps.And third, through a more diffuse “halo effect,” whereby its good deeds earn it greater consideration from consumers and others.
Previous studies on CSR have had trouble differentiating these effects because consumers can be affected by all three. A recent study attempts to separate them by looking at bribery prosecutions under America’s Foreign Corrupt Practices Act (FCPA). It argues that since prosecutors do not consume a company’s products as part of their investigations, they could be influenced only by the halo effect.
The study found that, among prosecuted firms, those with the most comprehensive CSR programmes tended to get more lenient penalties. Their analysis ruled out the possibility that it was firms’ political influence, rather than their CSR stand, that accounted for the leniency: Companies that contributed more to political campaigns did not receive lower fines.

其实你的翻译和参考书的翻译意思差不多，参考书是直译，你是意译。

前文提及CSR可以带来三个效应。通常难以区分消费者或其他人是如何受这些效应影响的。所以该研究选择公诉人/检察官作为研究对象，因为公诉人不会受到第一和第二种效应的影响，如果他们受影响则只能是受到了"光环效应”的影响。

consume在此有购买、使用之意，as 为介词，在此意为“作为”。公诉人不会作为调查的一部分而使用或购买某公司的产品，因此只可能受到光环效应的影响。你翻译为：公诉人在调查中不会消费。。。, 意思大同小异。as 后有part of...，不宜分析为时间状语，而只能分析为方式状语。但翻译的时候可以根据汉语习惯做一调整。