Physical Evidence Shows Defendant Had Sex with Alleged Victim

YoloCourt-25By Tiffany Yeh and Joanna Kwang

The first witness, Jonathan Sewell, a forensic analyst at the California Department of Justice (DOJ), resumed his testimony this morning in the Lang Her trial. Judge Richardson is presiding over this case, with Deputy District Attorney Jonathan Raven representing the People and Christopher Carlos representing the defendant.

P30 and acid phosphatase tests were done on the alleged victim’s panty liner. There were faint color changes, mainly at the center of the panty liner. The testing on the panty liner occurred on an overlay, and a picture of this overlay was shown by projector in the courtroom.

Filter paper is moistened and pressure is applied. Chemicals in both tests will react upon interaction with certain other substances. When this occurs, there is a color change. In the acid phosphatase test, dark purple shows a strong reaction, where the lighter the purple is from the test, the weaker the reaction.

A photo of test cards from the P30 test was shown. Four areas of the panty liner were tested and a control substrate (of unstained panty liner) were pictured on the photo. The control is used as a comparison.

The areas of the panty liner showed:

Area 1: positive faint band
Area 2: positive stronger band
Area 3: light phosphorescence, negative but no acid phosphatase
Area 4: negative, no fluorescence

An additional P30 test was conducted on the alleged victim’s underwear. All four areas of the underwear that were tested came out as negative.

The AP (acid phosphatase) test showed positive, P30 was positive, and evidence was found of seminal fluid on the panty liner.

A microscopic exam and chemical stains for semen were done on the panty liner.

Areas 1 and 3 of the panty liner had no evidence of sperm cells.

On area 4, two sperm cells and two possible sperm cells were found on the panty liner. Semen was present.

According to Mr. Sewell, the location of the stain and appearance is most consistent with vaginal fluid. Either direct contact or secondary contact of semen could have occurred (these two methods refer to the transfer of semen from one item to another in different fashions.)

The sexual assault kit from the hospital included vaginal, cervical and rectal areas’ samples. All the data that was tested on the samples were entered into the electronic system at the DOJ lab through a barcode.

The sexual assault kit contained:
Vaginal swabs (four) and smear slides (take one swab and run over the area);

Head hair sample (collected by a nurse); and

Oral swab (of the inside cheek of the alleged victim), later taken from a reference sample, which is later to be compared.

One of Mr. Sewell’s colleagues conducted DNA analysis on certain items. The bioscreening results were reviewed. The DNA is then compared to individuals. Then the items that are best for DNA processing are determined.

The oral swab, rectal smear and slides, and cervical swabs were tested.

Two oral swabs and the smear slide were prepared by the nurse. Two rectal swabs underwent AP, P30, and microscopic tests (all of the three tests came out negative).

Two cervical swabs of the alleged victim were obtained by the nurse. Cervical swabs were negative for AP and P30, and there were no sperm cells. No semen was detected.

These were described as fairly comprehensive tests, with fairly small cuttings from swabs used (thus, one swab can be tested further).

Therefore, if the defense requests, they can also send samples to a lab of their choosing.

Bioscreenings were conducted.

For the vaginal swabs, four swab cartons and one smear slide were in the kit. This includes four vaginal swabs.

Tests showed AP and P30 negative, with no semen detected. When questioned, the expert stated that it does not mean that no semen is present – very, very low amounts of semen cannot be detected by the test.

In the expert’s opinion, there was semen in the panty liner that came from vaginal fluid that was consistent with penetration and ejaculation.

The defense asked a line of questioning that sought to undermine the expert’s partiality, because the expert had communicated with DDA Raven through email and in person beforehand.

The expert had given Raven a list of questions that the prosecution should ask him (Sewell). The expert explained that these are questions he likes to be asked, that they help with the flow. He stated that he was aware of what the DA’s theory of the case is in general, and what the defense’s theory of the case is in general. The expert stated that he knew in a general sense why the case is being prosecuted.

The expert said he knows “very little” about the alleged victim, except from the hospital questionnaire and related documents. The defense brought up that the expert stated that he could be “a little stronger in my wording.”

The expert and the DDA met in person in early January. The patterning of fluorescence on the panty liner was something that the expert advised DDA about. To run the expert testimony slightly more smoothly, the expert advised DDA to show the jury the Bio 101 PowerPoint first, and then mention the patterning of fluorescence on the panty liner later. Hopefully this would avoid confusion, said Sewell.

The vaginal swabs were tested, the patterning on the seminal fluids was linear, and the AP (a fairly weak positive) and P30 tests were performed. There could be vaginal fluid (a fairly weak positive on the AP test). According to the expert, there were two fairly positive sperm cells and two possible sperm cells. The AP was a weak positive, with two sperm.

The argument is that sperm cells are present in pre-ejaculation. This is debated in biology literature.

One milliliter of a man’s ejaculate contains 10-50 million sperm cells. In a neat, direct ejaculate, one would expect many more sperm cells.

Acid phosphatase shows up in vaginal fluid, feces, breast milk, and occasionally urine, while P30 is either positive or negative (and can also be found in pre-ejaculate).

Chemical and microscopic exams were performed. Regarding pre-ejaculate or vaginal drainage, tests were inconclusive. A small cutting from each vaginal swab showed AP to be negative, found in high levels in seminal fluid – there was no color change. A larger cutting from one was negative for P30 (found in seminal fluid), with no sperm cells present. No sperm cells were found from vaginal testing.

The tests were run from  July 31 to August 1, in 2012.

The alleged victim’s green pajamas were analyzed under regular light and black light. The left exterior breast area of the pajamas showed some coloring with one of the types of light sources. But under the alternate light source, the pajama area did not show any coloring indicating anything. Food and chemical products or cleaning products can influence the presence of the coloring under the light. For the acid phosphatase test, all surfaces tested negative for both the interior and exterior.

In July 2012, vaginal smear slides were tested and no sperm cells were observed under the microscope.

Cervical smear slides showed no sperm cells observed, and the tests for seminal fluid and AP for cervical swabs came out negative.

Rectal smear slides showed no sperm cells and no semen detected, and for the rectal swabs, AP was negative, no sperm cells were observed (on a microscope slide) and P30 was negative. For microscopy, area 1 had no sperm cells and area 2 had two sperm cells and two possible sperm cells).

The sexual assault kit and panty liner, as indicated, were tested in July and August of 2012. The green pajamas were tested in December of 2014. The expert took the photo of the underwear interior with the panty liner removed. There is an area of light, very light red-brown staining in the center of the AP overlay (negative), from the interior of the underwear. Four cuttings from four areas were negative.

The ejaculate was neat – directly from the individual. A hypothetical posed from the prosecution to the expert was: Supposing a neat ejaculate from the individual, and the alleged victim had a tampon in (absorbing all the fluid), then there would be a low sperm count on the panty liner.

Forty-three hours elapsed before the sexual assault kit was tested. After about two days, sperm count shows a steep drop off or dilution.

Looking at the panty liner, one can’t tell whether it is drainage or pre-ejaculate.

The panty liner stain is consistent with vaginal drainage (this fluorescent area is consistent with normal menstrual fluid). The size of the stain shows that it is not consistent with pre-ejaculate. The patterning of the stain is diffuse and is in a circular pattern of fluid expansion.

Between depositing and smear versus direct contact with penis and panty liner, vaginal drainage is most likely. The center of the panty liner has a circular pattern and is weak.

Semen outside the body can last for many years afterward. Within a vagina, breakdown of semen can occur.

For the semen on the panty liner, distinguishing between semen or pre-ejaculate is not possible.

The next witness for the People was Heather Tomchick, an expert witness in biological screenings and DNA analysis. She is employed by the California DOJ, and she works as a criminalist in the crime lab, examining evidence from crime scenes to look for biological fluids.

Ms. Tomchick presented to the court a “Forensic DNA Analysis” PowerPoint which explained what DNA is, where DNA is found, the DNA extraction methods, and DNA analysis, among other topics related to her line of research for her job.

Tomchick stated that she received evidence from the Lang Her case back in April of 2013. The envelope that contained the panty liner was from her colleague, Jonathan Sewell.

She performed a DNA analysis on the panty liner. The AP overlay displayed areas where acid phosphatase was found. Mr. Sewell gave this information to Ms. Tomchick for reference to areas she may want to look further into.

The witness stated that the screening informs only if fluid is or is not present. The DNA, on the other hand, is able to indicate exactly what the fluids are and from which individuals(s) the fluid came. Although the screening test may not detect the presence of DNA evidence (a negative screening), she claimed this does not mean DNA evidence is not present – she noted that only a small portion of the panty liner was tested.

She further tested the panty liner by vigorously rubbing the top half of the panty liner with a swab that was wet with sterile water. A differential extraction of swabs was performed, and this was an attempt to separate the sperm cells material from the non-sperm material.

DDA Raven then asked Ms. Tomchick to summarize her conclusion from her DNA test, and she stated that “the DNA results provided shows Lang Her was the source of semen found on the panty liner.”

Ms. Tomchick examined the panty liner once again in October. She took a cutting from the panty liner from an approximate area where it was previously cut by Mr. Sewell. Further tests were then done.

About The Author

The Vanguard Court Watch operates in Yolo, Sacramento and Sacramento Counties with a mission to monitor and report on court cases. Anyone interested in interning at the Courthouse or volunteering to monitor cases should contact the Vanguard at info(at)davisvanguard(dot)org - please email info(at)davisvanguard(dot)org if you find inaccuracies in this report.

Related posts


  1. sisterhood

    How would this physical evidence differ if this young man was masturbating in his bed, alone, and a person later slept in the same bed or sat on the sheets of this same bed?

  2. Tia Will


    Good question. I think that this is where the distribution pattern becomes important. I think it very unlikely, although not impossible to get seminal fluid in this exact distribution from the sheets. However, it is also difficult for me to believe that this amount of fluid in this distribution demonstrates penetration given that no fluid or sperm were found in the vagina.

    There are actually two issues here. One is demonstration of penetration, or even direct skin to skin contact,  which remains unproven. The second would be whether or not the sexual activity ( what ever it involved) was or was not consensual.

    So far, given only the information presented here, there seems to be far more than reasonable doubt.

  3. sisterhood

    “However, it is also difficult for me to believe that this amount of fluid in this distribution demonstrates penetration given that no fluid or sperm were found in the vagina.”

    Interesting. Thank you.

    If this young man was wearing a condom, I assume the amount of fluid would be less in the distribution?

  4. Publicwriter

    sisterhood — “if this young man was [were] masturbating in his bed…” how could his semen be found on the inside of the victim’s panty liner?

    Tia Will — “There are actually two issues here. One is demonstration of penetration, or even direct skin to skin contact,  which remains unproven. The second would be whether or not the sexual activity ( what ever it involved) was or was not consensual.”  Think about this:  The victim was both on her period and had a tampon on.  Do adult women on their periods who have tampons inside them normally engage in consensual sexual activity (i.e., sex for pleasure)?  I don’t think so!  To your second point about “proving” the demonstration of penetration:  Where did the semen on the victim’s pantyliner come from?  Ms. Tomchick of the DOJ concludes from her DNA test that “the DNA results provided shows Lang Her was the source of semen found on the panty liner.”  What is that human anatomy that pantyliners cover?  Yes, you guessed it, the vagina.  Lang Her’s semen on the victim’s pantyliner is strong evidence that he penetrated.  The victim testified that Lang Her penetrated her.  Lang Her, along with his attorney, has had a tendency to go back and forth in their arguments:  changing Lang Her’s testimony from denying the rape altogether to claiming that the rape was consensual.  I hope that intelligent folks, you included, can see through this kind of legal maneuvering and recognize the guilt and hypocrisy in it.

  5. Publicwriter

    Davis Vanguard and, especially Tiffany Yeh and Joanna Kwang, thank you for providing the public your service and for the fairly detailed coverage of this case.

Leave a Reply

X Close

Newsletter Sign-Up

X Close

Monthly Subscriber Sign-Up

Enter the maximum amount you want to pay each month
Sign up for