It is one of the sources of defects.

Due to the less time for finishing a project or having less number of resources like coders,developers etc may cause this defect.

Due to the stress of being completed on time the software developers may omit some cases without proper testing.

These may result in the origin of defects.

Or else he might think that he did the correct thing at that particular point due to oversight.

The software engineer might know what to do and how to do it.

But he makes some mistakes while coding or testing.

These may be because of lack of education or being oversight.

It is necessary to follow a particular process  when we are developing a software product or anything else.

Some times the process used by the software engineer misdirected his/her actions.

Impact on software artifacts due to sources of defects:

These may cause errors to the code.

Results in faults also known as defects.

And results in the failure of the software.