Finding, developing and maintaining sources are crucial for an investigative journalist. The most important, reliable and vivid sources are usually witnesses, people with first-hand experience or are otherwise directly involved in a story. You identify witnesses by combing through the names of people present at the scene, or simply buttonholing those while you are there. If people claim to have been present or involved, you must verify that they were. If a witness has experienced the story, he or she would likely be a valuable asset to you. When reporting on what you have observed at the location of a story, you become a very important witness yourself.
And each story you write should expand the scope of your network. Often, this happens organically in the course of reporting. But if you are working on a specific project, you should be proactive in building a network of highly relevant and credible sources. Do not neglect your journalistic colleagues; they may have valuable personal connections, but if rivalry on a story is intense, you may not wish to share story details.
You can also search for people publicly associated with your story subject. Consider organisations like sports clubs, religious organisations or charities. Remember that such people, because they are in some kind of relationship with the subject, may have a disposition or attitude towards him or her. Factor this into your enquiries. Look for people who were previously associated with the subject: Ex-partners in business, former spouses, employees, doctors, teachers, or former police or army officers. People with whom the subject was in a known dispute or in litigation can also be very important witnesses, but, again, remember that their emotions and attitudes will colour what they tell you. Development researcher Joe Hanlon calls this ‘finding the woman who knows’.