There are a number of times in which companies will have to conduct internal investigations. These investigations can be triggered by a number of different actions, including mistakes made by employees, as well as by concerns about expenditures, or allegations of fraud or negligence. When choosing to conduct an investigation, the company may choose to assign people from inside the company to investigate or to hire outside specialists. The latter approach has many advantages.
Perhaps the main advantage of hiring outside specialists is that they generally know what they're doing. These specialists are trained to conduct the specific work for which they have been hired. By contrast, when detailing members of a company to conduct an investigation, they may be attempting to carry out tasks for which they have little or no training.
Lack of Bias
In addition, an outside party will have little bias when attempting to assign blame for any wrongdoing. The specialists' goal is to identify what mistakes were made, who made them, and what can be done to prevent them from happening again, without regard to who will be affected by their findings. By contrast, employees of the company being investigated may have prejudices for or against fellow employees.
Honesty and Confidentiality
Because the specialists are hired to do a particular job, with their reputation riding on their effectiveness, they can be expected to remain both trustworthy and confidential. Any information they gather will not be revealed to employees who do not need to know it, nor to outside parties. By contract, internal employees could leak to co-workers, who could let the information fall into the wrong hands.
In some cases, hiring specialists is actually more cost-efficient than attempting to conduct an investigation in house. This is true for two reasons. First, by outsourcing the investigation to people who have conducted them before, the investigation will likely be concluded more quickly. Secondly, leaving the outside parties does not divert employees from their primary tasks, this allowing them to continue adding value to the company.