News can make for some odd, and at time competing instincts in journalists: The responsibility and the opportunity.

Look at a story like the trial of Casey Anthony, the Florida mother who is accused of killing her 2-year-old daughter Caylee in 2008. A case like this typically pushes stations to pull out all the stops for coverage, especially if it’s in your backyard. At the same time, with a story that has captivated the public the way this one has, there’s also a chance to capitalize on that attention.

WESH-TV, the NBC affiliate in Orlando, did both: not just blowing out its coverage to capture all aspects of the trial, but also launching a 99-cent iPhone app for trial updates. And at a time when even the strongest newspapers and broadcasters typically offer their apps for free, WESH’s paid app appears to be a big success. It reached the top spot in paid iPhone news apps over the weekend, and it’s currently residing at the No. 2, ahead of popular apps like Instapaper.

“I don’t think we would have predicted it would be the No. 1 selling app in the App Store,” Gabe Travers, digital media manager for WESH.com, told me. And whatever one thinks about the way trials like this one are covered in America, WESH’s experience does seem to indicate there can be a business opportunity when a local story goes national.

When I spoke to Travers, he said their instinct from the beginning was to expand the ways they cover the trial and deliver news to the audience. “It was a no-brainer to make something like this for folks interested in the trial,” he said. Travers declined to disclose how many downloads the app has generated. Under Apple’s sales model, WESH would net about 70 cents per download.

Launched in April, the app is a collection of the trial reporting from WESH, including access to their liveblog, breaking updates, court documents, photos, and video recaps, along with a mix of courtroom footage and packages produced by the station. One thing missing from the app is live video from the courtroom, which proved to be more tricky and costly to add to the product, Travers said. While live video may seem like the biggest draw, one surprising attraction in the app has been the documents. “There’s more than 20,000 pages of evidence released. You’d think documents would be something dry for folks, but people have a huge interest,” Travers said. “They like stories about the evidence as much as they like the documents themselves.”

With national (and possibly international) interest in the trial, WESH is aiming to reach an audience that has likely never heard of the station. Perhaps as a result, the Casey Anthony Updates app isn’t strongly branded with the station’s identity; the app’s description in iTunes makes no mention of WESH, and the app features only a few small references. (In the App Store, the app’s vendor is listed as Hearst Television, WESH’s corporate parent.) “There’s a huge amount of local interest and a huge amount of national interest. For us, we want to be the go-to source for information on the trial,” he said.

That strategy also holds true outside the app. On WESH.com, there’s a livestream from the courtroom, along with a liveblog and a collection of #CaseyAnthony Tweets curated using ScribbleLive. Outside the site, there’s a Casey Updates Facebook page, created before the start of the trial, that delivers news from the station to more than 70,000 people. On Twitter, they’re live-tweeting the case — and, maybe more interestingly (if not just hilariously), the judge. On the JudgePerrySays account they deliver the best quotes (from the procedural to the culinary) of the day from Judge Belvin Perry, who is presiding over the case.

With all their coverage, but particularly the app, Travers said they wanted to be careful to not be seen as sensationalizing, or worse, trying to profit off such a tragic case. The decision to make the app, and charge for it (the station also has a free WESH news app), was guided by the idea that they could offer up a premium product for people interested in the case that would be able to help meet the additional expenses of covering the trial.

Travers said he thinks their success with the app is proof that media outlets of all sizes can innovate in how they deliver news and create new revenue streams. For WESH — like any station, newspaper, or website — the first step is finding where the public’s interest in stories and your outlets reporting resources meet. The second step is finding time to build something, Travers said.

“We had a good amount of time to plan, know what our strategy is, time to get our ducks in a row, to get the timelines and documents,” he said. “When we came to this point in the trial, we had done lots of planning and were ready for what it would entail.”