Cassandra Do was known for being ‘very discerning’ about her sex trade clients. So how did she end up dead in her bathtub?

Cassandro Do was a sex trade worker with a reputation for being careful.

The 32-year-old didn't use drugs or work the streets. She carefully screened who got into her downtown lowrise apartment on Gloucester Street near Church, which was decorated in a French classical style.

Do attracted clients through a website and advertisements in the back pages of a weekly newspaper.

Before a client got into her apartment, she screened him, either on the phone or over coffee.

She was very discerning on her clients," said acting Det. Sgt Stephen Smith of Toronto police in a video prepared by police on the case.

She had not completed a male-to-female sex change and was open about this with her customers, so there would be no surprises.

Customers knew her as Tula." She was small, at five-foot-two, slender and had luxurious raven hair.

She had breast implants and a delicately reshaped nose.

She had the surgery after moving to Toronto from Kitchener, where she had worked as a nurse's aide at a seniors home.

I didn't know that there was that many men that are attracted to transsexual until I moved to Toronto," she told makers of a 2002 documentary called Skin Deep."

And it was very nice because I felt like I'm not a freak anymore. There's actually people out there that find myself attractive...

I think most people in the public when they look at me, see someone maybe attractive and maybe a little bit different."

In Toronto, she did well enough financially in the sex trade that she was able to help out relatives with their bills.

Eventually, she planned to earn enough money to complete her sex change and become a nurse, she told the documentary.

I think I'm looking forward to getting back to nursing because I think people can look at me and say, I see a female' instead of what they saw before, which is a young man who's struggling, trying to be female. And I think the more feminine I look and the surgery that I've had has helped me achieve that."

She was born to an American soldier and a Vietnamese mother, and moved to Canada when she was eight.

Growing up, when I look at myself in the mirror, I just felt very sad and confused," she said in the documentary. It was very upsetting that I see someone that looks male and I didn't feel that way...

It was very difficult in high school. I was teased and made fun of ... I was very much of a loner. I didn't feel like I belonged anywhere. I didn't fit into any special group or anything.

I don't think I realized that I was transsexual until I was about 16. That's when I realized that I was attracted to men, but I wasn't like other gay men - I didn't want to be male, I felt female."

She moved to Toronto at a particularly low point in her life, after she felt rejected by her boyfriend and parents.

I felt like I had nothing to live for. And I seriously wanted to end my life, and it was only after failing to do so that I moved to Toronto and wanted to get away from everything that was hurting me. And I felt like Toronto would be a much more understanding and accepting place...

When I first moved to Toronto, I very much wanted to get back into nursing. I called and applied for many places for work. And the response is, Oh, yes, we're hiring. Please come by. We need someone to work soon.' And when I show up because of my appearance right away, I was told that we have already hired somebody or we will call you and they never end up calling me back."

For a time, Do lived in the West End, where she enjoyed goth bars. She moved to the downtown to get away from a client who wouldn't stop harassing her.

She eventually came to realize that even surgery could only do so much.

I don't think any surgery that I have is gonna change some people mind. There are some people out there that's not going to like me, the fact that I'm transsexual and I've experienced all kinds of prejudice from just regular strangers to law enforcement people and whatnot, and it's very sad, but that's the way it is."

On Monday, Aug. 25, 2003, Do had plans to see a new client at 4:30 in the afternoon. She had another date" scheduled for that evening, and then a meeting with relatives.

The 4:30 date must have been articulate to be allowed inside her door.

He was able to talk her into seeing her for the first time," Smith said.

Something went horribly wrong almost immediately after they met.

Her lifeless body was found by a relative that evening, in her bathtub. She had been strangled.

Her killer had dominated and attempted to humiliate her in the final moments of her life, police concluded. That included raping her before she was strangled.

Police probed whether Do's killer was the same man who murdered Lien Pham, a 39-year-old widow and sex worker who was strangled less than two months later.

Pham was found dead in an 18th-floor apartment on Mabelle Avenue in Etobicoke on Oct. 13, 2003 - Thanksgiving Monday.

Pham was a mother of two whose husband had been the family's breadwinner until his death.

She didn't speak English well enough to qualify her for much work, but she was a good earner in the sex trade, sometimes seeing seven clients a day.

Her escort agency clients often knew her as May-Ling."

DNA evidence was found on Pham's body, but it didn't match up with samples taken from any other crime scene, Smith said.

However, DNA found on Do's body connected her attacker to the 1997 sexual assault of a sex worker close to Do's apartment.

The 1997 sexual assault victim was still alive at the time of Do's murder. She managed to flee into a bathroom after she was raped, and locked herself inside until the attacker left.

That earlier victim described her attacker as a powerfully built, clean shaven Black man with closely cropped hair. Descriptions of his height varied from six-foot-two to six-foot-six.

He brought handcuffs to her apartment.

Police probed plenty of theories about the man whose DNA was linked to the two attacks.

Could he live in the area? Work there? Was he a mobile predator?

It could be anything," Smith said.

Investigators ran his DNA through a national data bank for offenders, as well as in foreign data banks, with no success.

Smith won't go into details, but says he believes there is someone who could identify Do's killer.

We know that that person knows," Smith said.

Meanwhile, investigators can't help but wonder where Do's killer went. Did he die? Settle down? Keep committing crimes without leaving his DNA?

He could be living an otherwise normal life," Smith said.

And where did he get the handcuffs?

Was he a security officer?" Smith asked. Did he work in law enforcement? Was he a bouncer in a club?"

Do's life ended at a relatively calm stage of her life, when she had no plans to further alter her appearance with more surgery.

She still had plenty of plans for the rest of her life.

I think I'd have to work with my inner self and just be happy with myself and other people that are around me and not concentrate so much on cosmetic surgery itself," she said in the documentary.

For me, I think what would make my life totally complete and happy is being in a relationship with someone who is loving and being in nursing field that I truly love and just having a normal life."

The Do and Pham murders remain unsolved.

Peter Edwards is a Toronto-based reporter primarily covering crime for the Star. Reach him via email: pedwards@thestar.ca