Energy giant BP (BP -0.67%) is still paying for its mistakes made stemming from the tragic rig explosion in the Gulf of Mexico more than three years ago. Its public image has yet to be restored, its share price and dividends are still not where they were pre-spill, and it's paid billions in damages so far. Unfortunately for the company, BP recently suffered an unfavorable court ruling that it was counting on, to help keep costs down.

The recent court decision against BP is a disappointment, but investor attention should be squarely affixed on a separate court matter that carries much more significant impacts.

No proof of losses required
BP failed in its efforts to require businesses to submit proof of financial losses stemming from the 2010 oil spill. BP accepted a previous agreement in which certain businesses could be compensated if their losses reflected certain patterns, and the company is now forced to live with its prior arrangement. This is an important consideration, since this settlement has already cost BP billions. BP has paid $3.8 billion to more than 40,000 claimants.

BP clearly has the most to lose of all the companies involved in the Gulf spill, as many others received penalties amounting to little more than a slap-on-the-wrist. That stands to reason, of course, since BP was the operator of the rig that exploded. Still, BP investors face a pronounced risk that neither Transocean (RIG -3.89%) nor Halliburton (HAL -1.04%) investors need to concern themselves with.

Transocean was the owner of the Deepwater Horizon rig in question, and it's largely back to business as usual. Transocean pleaded guilty to violating the Clean Water Act and was forced to pay $400 million, in addition to other penalties, earlier in 2013. All the while, Transocean's underlying business has strengthened considerably this year, thanks to the boom in global deep-water oil drilling. Transocean booked more than $1 billion in net profit through the first nine months of 2013, entirely reversing the $660 million net loss in the same period last year.

Meanwhile, Halliburton was the contractor that provided cement used in construction of the well, and it's completely past any damaging effects. Halliburton's $200,000 penalty was a pittance to a company of its size. Its third-quarter revenue set a record at $7.5 billion, and the company increased its dividend by 20% in November.

BP has more pressing matters ahead
While BP's unfavorable court ruling is indeed a disappointment for the company, investor attention should be focused on the ongoing civil trial. That's because the civil trial is much more important financially to the company. There are literally billions of dollars at stake depending on how the civil trial unfolds and whether BP is found guilty of gross negligence.

The outcome of the civil trial becomes even more important because of the extremely wide range in likely penalties the company may face. BP faces up to $18 billion in penalties if found guilty of gross negligence and if 4.2 million barrels spilled into the Gulf. If BP is not found guilty of gross negligence and its assertion that a lower amount of oil spilled is upheld, the tab will be closer to $3 billion. Clearly, the possibility of an additional $18 billion in penalties is the one major remaining overhang on BP, and represents a huge consideration for investors going forward.

Keep your eyes on the civil trial
While BP's recent court disappointment represents a setback, it's a relatively modest concern in comparison to the ongoing civil trial. That's what investors need to pay close attention to in the months ahead, as it will have the greatest impact on BP's ability to get back to its core strategic initiatives. BP's valuation remains weighed down, and its exploration and production growth are significantly hampered by the uncertainty of what it might pay once the civil trial concludes. As a result, the civil trial is what investors should keep focus squarely on in the first few months of 2014.