凭借独到的刑事侦查与鉴识技术，李昌钰先后在美国各州与全球47个国家协助破获8000多起，参与过碎木机杀人案、小肯尼迪强暴案、尼克松“水门事件”、辛普森杀妻案等大案。

I am Liuis from China. I'm always confused with the words ''objective'' and ''purpose''. I looked up in some dictionaries but still not quite sure. Thanks for your help in advance. Best regards.