Knoxville (WVLT) -- On the back of trucks, billboards, fliers, web-pages, and even on national TV, America saw a sketch of a man police called a person of interest in the murder of Johnia Berry.

Then on Monday, after 33 long months, we all saw a mug shot of the man police say is responsible for the December 2004 murder.

For many the side by side comparison is rather remarkable, even for the woman responsible for drawing it.

We sat down with the crime scene technician to find out what goes into creating such an important part of an investigation.

"I think it was a real close sketch," said Angela Verner, a crime scene technician.

Those are the only words the sketch artist uses to describe the drawing she composed for the Johnia Berry murder investigation.

But she can show, in detail, how she gets from a blank screen, to a complete sketch that oftentimes solves a crime.

"I think they are very important if the sketch is close," Verner said. "That is what brings clues to us, people calling with tips."

The witness is obviously key.

"I'm only doing what they are giving me," she said. "I have no clue what it is suppose to look like in the end"

Getting close to that mental picture in their mind, can be quite a challenge, even if they get a good look, or personally knows the suspect.

"There is always some similarity, one or two things, but sometimes everything else is off," she said.

Age, race, and gender questions come first.

The next question she asks is "what do you remember most"?

Usually, it's the eyes.

"Sometimes we'll pick four of five different ones before they say, that's close," she said.

But close isn't good enough.

Verner often spends hours on one feature before moving to the next.

"If they say this is kind of it, but kind of not, we're going to go through every option to see if we can find something better ," she said.

It's a tedious task, that thanks to technology requires little artistic ability, but lots of patience.

"The main thing is to let them have the time they need," she said. "Sit with them, don't rush and if it takes hours then it takes hours"

Verner says it's much harder to create a composite of a female than a male.

She also thinks it's very important that if you find yourself as a witness in a situation, you should remember certain things before others.

Verner says that chances are you will remember a persons age, race, and gender. She says for a face composite, it's really important to focus on specific features if you can.

Things like a persons face shape, nose size, eye shape and the look of their forehead and hairline are all very important in getting an accurate sketch. Something as simple as the shape of a chin can change the entire look.