An article posted in the National Law Review on January 31, 2010, titled "Top 5 Pitfalls to Avoid When Conducting Workplace Investigations" by employment attorney Julie Vogelzang is worth the read.  She lists and discusses the following pitfalls:

PITFALL NO. 1:  Failing to Promptly Begin the Investigation

She notes that "one of the worst things a company could face is a jury trial where a juror believes that the companied lagged in looking into the issues, thus leading to the potential for ongoing misconduct that was not stopped immediately."

PITFALL NO. 2:  Failing to Use an Experienced and Neutral Investigator

She notes that some "employers err if they randomly assign the investigation to someone without experience [because] . . .  the employer can face potential exposure for the failings of the investigator, in the form of claims of an inadequate investigation or punitive damages aimed at punishing the employer."

PITFALL NO. 3:  Punishing the “Victim”

She notes that it is the "better practice to temporarily transfer or suspend the accused with pay pending the investigation. This way, the person bringing the complaint is not punished or put in any disadvantaged position for having come forward."

PITFALL NO. 4:  Not Having a Reporting Structure in Place

She notes that "it is prudent to set up an ‘investigation team’ at the outset. This is so that the investigation and any actions taken do not fall exclusively on the shoulders of one person. If there are layers of management involved, issues can be vetted by a group rather than one person, and any subsequent claims against the investigator of wrongdoing, lack of thoroughness, bias, etc. are significantly minimized."

PITFALL NO. 5:  Promising Confidentiality

She notes that the "investigator will be reporting the statements to management; they may be sharing the statements with other witnesses so that a thorough investigation can be conducted; and if there is ever a lawsuit brought, the statements will likely need to be disclosed at that time."

I do appreciate the idea of an investigative team approach; however, only one employer I have ever worked with utilized it– the United States Postal Service ("USPS").  The USPS has an EEO Analyst (working from an isolated department, who has no knowledge of the parties involved) review each investigative report prepared by the EEO investigator before the "Final Report" can be submitted.  The Analyst tries to make sure there are no holes in the investigation, for example, have all relevant questions been asked, have all relevant witnesses been interviewed, and have all relevant documents been obtained.  While this may lengthen the process somewhat, potential claims against the investigator of wrongdoing, lack of thoroughness, and bias can be minimized.