Here's the problem if you rely on trend and overall statistics to try and prove some disparity. They can be countered by more statistics.
The statistics show that for every combination of white / black interracial crime that white on black crime is the lowest. So the implication that white police officers are intentionally killing black teenagers would be in stark contrast to the general pattern within the population as a whole which they of course come from. I'm not saying that it's not possible, just that it doesn't fit the pattern. Of course it's possible that all the racist whites decide to become police officers so they can shoot black kids ... but that seems a stretch - the number of shootings is pretty low to make all that effort and intervening work in law enforcement sound realistic.
Sadly, the figures show that blacks are disproportionately more likely to be committing violent crime so is it a surprise that the disparity then feeds through into law enforcement incidents involving them? (given that apprehending people who commit crimes is their job).
From Bureau of Justice Statistics (based on FBI figures for 1980-2008)
Blacks were disproportionately represented among homicide victims and offenders
- In 2008, the homicide victimization rate for blacks (19.6 homicides per 100,000) was 6 times higher than the rate for whites (3.3 homicides per 100,000).
- The victimization rate for blacks peaked in the early 1990s, reaching a high of 39.4 homicides per 100,000 in 1991.
- After 1991, the victimization rate for blacks fell until 1999, when it stabilized near 20 homicides per 100,000.
- In 2008, the offending rate for blacks (24.7 offenders per 100,000) was 7 times higher than the rate for whites (3.4 offenders per 100,000).
- The offending rate for blacks showed a similar pattern to the victimization rate, peaking in the early 1990s at a high of 51.1 offenders per 100,000 in 1991.
- After 1991, the offending rate for blacks declined until it reached 24 per 100,000 in 2004. The rate has since fluctuated, increasing to 28.4 off enders per 100,000 in 2006 before falling again to 24.7 off enders per 100,000 in 2008.
The report has many more crime stats and trends. I couldn't get Table 1 to copy but it's worth looking at too particularly the offending rates vs population rates.
Also, if you look at things by age, teens are far more likely to be committing crimes. So put the two sets of figures together and "black teens" becomes a large group that is disproportionately represented in both the crime statistics and the incidents involving law enforcement which then seems less surprising.
http://www.bjs.gov/content/pub/pdf/htus8008.pdf
The bottom line is - if you are going to cite statistics as 'evidence' then they need to be complate and comprehensive to provide the full picture. I actually think the police are more likely to shoot black suspects but not to the extent that is claimed or because they are black per-se ... it's possible that socio economic factors, differences in attitudes, responses and behavior and things like the three strikes rule + previous offenses make those from some groups more likely to run / resist arrest etc... which is then going to feed into the figures.
The figures are a symptom, they are not proof of anything or a judgement other than that is a count of what has happened. We need more than the figures alone to be able to say "why" anything happened and again, the only way to do that is by having an investigation of each incident to determine the cause and if there is any fault or not.