"Sell in May and go away." We've all heard that market adage. Fact is, it's anyone's guess whether that's good advice in 2017.

Even though investors are starting to feel a little anxious about stocks, the fact of the matter is that, as long as the big S&P 500 index scrapes up against all-time highs, there's not a whole lot of reason to bet on a sudden shift in the broad market's trajectory right now.

But even if the S&P continues charging higher from here, we're likely to see a meaningful chunk of this market not participate in the rally. Some might even be downright "toxic" to your portfolio. Avoiding those laggards might be even more important for your portfolio's performance this year than picking out the leaders.

To find the stocks to avoid, we're turning to the charts for a technical look at three you should consider selling here ...

Technical analysis is a way for investors to quantify qualitative factors, such as investor psychology, based on a stock's price action and trends. Once the domain of cloistered trading teams on Wall Street, technicals can help top traders make consistently profitable trades and can aid fundamental investors in better entry and exit points.

Just so we're clear, the companies I'm talking about today are hardly junk.

By that, I mean they're not next up in line at bankruptcy court--and many of them have very strong businesses. But that's frankly irrelevant to what happens to their stocks; from a technical analysis standpoint, sellers are shoving around these toxic stocks right now. For that reason, fundamental investors need to decide how long they're willing to take the pain if they want to hold onto these firms in the weeks and months ahead. And for investors looking to buy one of these positions, it makes sense to wait for more favorable technical conditions (and a lower share price) before piling in.

So, without further ado, let's take a look at three "toxic stocks" to sell--and when to sell them.

Lions Gate Entertainment

Up first on the list is movie studio, Lions Gate Entertainment Corp. (LGF.A - Get Report) (LGF.B - Get Report) . Lions Gate has been under pressure in recent months, shedding about 12% of its market value from February's highs through today. The bad news is that shares could be about to kick off a second leg lower.

That's because Lions Gate has been forming a classic descending triangle pattern, a bearish continuation setup that signals more downside ahead. The descending triangle is formed by horizontal support down below shares at $22.80 (in the case of B shares), and downtrending resistance to the topside. As Lions Gate bounces between those two technically important price levels, shares have been getting squeezed closer and closer to a breakdown through that support level. Once that happens, it's time to be a seller.

The lower highs in relative strength, the indicator down at the bottom of Lions Gate's chart, signals a high risk of more downside ahead. Buyers beware.

EOG Resources Inc.

Meanwhile, price action doesn't get much simpler than what we're seeing in shares of $56 billion energy stock EOG Resources Inc. (EOG - Get Report) . In a nutshell, EOG has been stuck in a well-defined downtrend all year long, and it's still stuck in that downtrend. Don't get fooled by the rebound in shares in the past couple of days in EOG--shares are testing their price ceiling again right now.

EOG's long-term downtrend is defined by a pair of parallel trendlines that have identified the high-probability range for shares to stay stuck within. In other words, every time this stock has rallied up to test trendline resistance, shares have been unceremoniously swatted lower in reaction. Now, this stock is in position to have it happen for a fifth time.

As long as EOG remains below its 50-day moving average (a proxy for trendline resistance on the chart), you don't want to own it.

Crown Castle International Corp.

Crown Castle International Corp. (CCI - Get Report) , on the other hand, has actually been a great performer in 2017. Shares are up about 10% so far this year, beating the big averages in the process. But investors might want to think about taking some of those gains off the table at this point.

That's because Crown Castle is forming a head-and-shoulders top, a bearish reversal setup that signals exhaustion among buyers. The pattern is identified by two swing highs that top out at approximately the same level (the shoulders), separated by a higher high (the head). The sell signal triggers when Crown Castle's neckline gets materially violated--that happens at the $93.50 price level, a line in the sand that's very close to being tested today. 

If CCI materially violates $93.50, look out below.

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At the time of publication, author had no positions in the stocks mentioned.